Hot and Cold Therapy for Face: How Temperature Contrast Transforms Your Skin
⚡ Bottom Line
Heat and cold act on the skin through opposite but complementary vascular mechanisms. Heat (thermotherapy) induces vasodilation — dilating blood vessels, increasing dermal blood flow, temporarily increasing skin permeability, and priming fibroblasts for maximum response to active ingredients and microcurrent stimulation. Cold (cryotherapy) induces vasoconstriction — constricting blood vessels, reducing capillary fluid leakage, decreasing inflammation, firming tissue, and reducing pore appearance. Used in sequence — heat first to open and prime, cold after to seal and consolidate — temperature contrast therapy produces compounded skin benefits that neither achieves alone. The Elevaure 7-in-1 (8 Modes) Hot & Cold Face & Neck Beauty Device delivers 3-level thermotherapy (Mode 1: 46°C / 114.8°F, Mode 2: 42°C / 107.6°F, Mode 3: 38°C / 100.4°F) and 2-level cryotherapy (Mode 4: Full intensity, Mode 5: Half intensity), providing both ends of the therapeutic temperature range in a single device designed for the contrast protocol.
The Dermal Science of Temperature — Why Hot and Cold Do Different Things to Your Skin
Heat Opens. Cold Seals. Used in Sequence, Temperature Contrast Is the Most Underutilized Tool in Skincare.
Heat and cold act on the skin through opposite but complementary vascular mechanisms. Heat (thermotherapy) induces vasodilation — dilating blood vessels, increasing dermal blood flow, temporarily increasing skin permeability, and priming fibroblasts for maximum response to active ingredients and microcurrent stimulation. Cold (cryotherapy) induces vasoconstriction — constricting blood vessels, reducing capillary fluid leakage, decreasing inflammation, firming tissue, and reducing pore appearance. Used in sequence — heat first to open and prime, cold after to seal and consolidate — temperature contrast therapy produces compounded skin benefits that neither achieves alone. The Elevaure 7-in-1 (8 Modes) Hot & Cold Face & Neck Beauty Device delivers 3-level thermotherapy (Mode 1: 46°C / 114.8°F, Mode 2: 42°C / 107.6°F, Mode 3: 38°C / 100.4°F) and 2-level cryotherapy (Mode 4: Full intensity, Mode 5: Half intensity), providing both ends of the therapeutic temperature range in a single device designed for the contrast protocol.
Thermotherapy, Cryotherapy & Temperature Contrast Therapy
Temperature-Based Skin PhysiologyThermotherapy is the therapeutic application of heat to tissue. At the skin level, heat causes vasodilation — the dilation of blood vessels — which increases local blood flow, raises tissue temperature, increases cellular metabolic activity, and temporarily disrupts the lamellar structure of the stratum corneum lipid matrix, increasing skin permeability. The result: better-oxygenated fibroblasts, increased dermal receptivity to active ingredients, and enhanced response to electrical stimulation (microcurrent). The Elevaure device delivers three heat levels: Mode 1 (46°C / 114.8°F + Red light), Mode 2 (42°C / 107.6°F + Cyan light), Mode 3 (38°C / 100.4°F + Yellow light) — dermal blood flow increases approximately 3–5x above baseline at the highest heat level.
Cryotherapy is the therapeutic application of cold to tissue. Cold causes vasoconstriction — the constriction of blood vessels — which reduces blood flow, lowers tissue temperature, reduces metabolic activity, and tightens the extracellular matrix. The result: reduced capillary fluid leakage (less interstitial fluid accumulation), decreased inflammatory mediator activity, reduced pore appearance, and temporary tissue firming from matrix contraction. The device delivers two cold levels: Mode 4 (Full intensity + Green light) and Mode 5 (Half intensity + Blue light).
Temperature contrast therapy — alternating heat and cold in sequence — exploits both mechanisms. The vascular 'pump' created by vasodilation followed by vasoconstriction increases lymphatic and venous clearance of metabolic waste from the tissue, while the sequence primes skin for active ingredient delivery (heat phase) and then locks in the treatment effects (cold phase).
Why Skincare Products Work Better With Heat — and Why Cold Is the Missing Final Step
Active skincare ingredients (retinol, vitamin C, peptides, hyaluronic acid) applied at room temperature to non-primed skin produce inconsistent results — limited penetration beyond the epidermis means the ingredients are not reaching the dermal layer where collagen synthesis, fibroblast activity, and structural skin changes occur. Simultaneously, post-treatment redness, inflammation, and puffiness from microcurrent or active ingredient use has no targeted resolution step.
The stratum corneum is designed to be a barrier — it prevents water loss and keeps external substances out. At room temperature, most topically applied actives remain in the epidermis or upper dermis at concentrations too low to produce the clinical effects demonstrated in research (which typically uses delivery systems that bypass the barrier). Without heat pre-treatment, the full potential of high-quality serums and active ingredients is not realized. Cold therapy is similarly underused as a post-treatment consolidation step — most routines end with product application on warm skin, leaving inflammatory mediators and post-stimulus redness unaddressed.
Room temperature skin → intact stratum corneum lipid barrier → limited active ingredient penetration → epidermis-only effect → insufficient dermal stimulus → suboptimal results. Post-treatment: inflammatory response from actives/microcurrent → no vasoconstriction step → extended redness and puffiness → incomplete treatment cycle.
Heat pre-treatment (Mode 1: Red light + 46°C / 114.8°F + Vibration, 1–2 min) before active ingredient application and microcurrent: temporarily fluidizes the stratum corneum lipid matrix, increasing permeability and dermal delivery. For sensitive skin, Mode 2 (42°C) or Mode 3 (38°C) offer gentler heat levels. Cold finishing (Mode 4: Green light + Full intensity, or Mode 5: Blue light + Half intensity, 1–2 min) after treatment: vasoconstriction reduces post-treatment inflammation, closes the treatment cycle, reduces pore appearance, and consolidates the firming effect of the full protocol. Mode 8 (Auto-Sensing) activates on skin contact and shuts off automatically 1 minute after leaving the skin. The complete heat→treatment→cold sequence takes 10–14 minutes total and produces compounded results at each step.
Three Signs Your Skincare Routine Is Missing Temperature
You're applying the right products in the wrong conditions. Temperature is the delivery mechanism your routine is missing.
Temperature is the most underutilized variable in skincare. It costs nothing to add and amplifies every other step in the routine — yet most protocols apply products to room-temperature skin and skip the cold finish entirely.
- Expensive Serums That Sit on the Surface Instead of Absorbing — High-quality retinol, vitamin C, or peptide serums applied to room-temperature skin that bead up, sit on the surface, or absorb slowly — producing visible results far below what the ingredient concentrations should deliver. The stratum corneum is functioning as designed: keeping external substances out. Without heat pre-treatment to temporarily fluidize the lipid barrier, even well-formulated actives remain in the epidermis at concentrations too low to produce meaningful dermal effects. The investment in quality ingredients is wasted if the delivery mechanism doesn't reach the layer where those ingredients work.
- Post-Treatment Redness That Lingers for Hours — Redness, warmth, and minor puffiness after microcurrent, chemical exfoliants, or active ingredient use that takes 1–3 hours to resolve — leaving skin looking reactive rather than glowing. This is post-treatment vasodilation and inflammatory mediator activity with no targeted resolution step. Cold therapy applied immediately after treatment produces rapid vasoconstriction that closes this response within minutes — reducing redness, calming inflammatory activity, and producing the firm, even-toned appearance that should follow a good treatment.
- Enlarged Pores That Don't Respond to Topical Treatments — Visible pores — particularly across the nose, cheeks, and forehead — that topical pore minimizers and niacinamide products haven't meaningfully changed. Pore size is primarily determined by genetics, sebum production, and skin elasticity around the pore opening. While topical ingredients can reduce sebum and mildly improve elasticity, the fastest and most reliable mechanism for reducing pore appearance is vasoconstriction from cold therapy — which firms the tissue immediately surrounding each pore, making the opening appear visibly smaller. Results are temporary (15–30 minutes) but consistent with each cold application, and can be used strategically before photography, events, or makeup application.
Temperature Specifications — Hot & Cold Therapy Protocol
7-in-1 (8 Modes) Hot & Cold Device — 3-Level Thermotherapy & 2-Level Cryotherapy Temperature Contrast Protocol
Mode 1 (Red light + 46°C / 114.8°F + Vibration) delivers the highest heat level — within the therapeutic thermotherapy range that induces vasodilation and skin permeability increase. Mode 2 (Cyan light + 42°C / 107.6°F) and Mode 3 (Yellow light + 38°C / 100.4°F) offer progressively gentler heat levels for sensitive or reactive skin. Red, cyan, and yellow light simultaneously activate photobiomodulation targets. Modes 4–5 deliver cryotherapy: Mode 4 (Green light + Cold Full intensity) and Mode 5 (Blue light + Cold Half intensity) — within the range that induces vasoconstriction, reduces inflammation, and produces temporary tissue firming. The device is designed for sequential use: heat (Modes 1–3) primes the skin before active ingredient application and other treatment modes; cold (Modes 4–5) closes the treatment protocol after microcurrent, LED, or gua sha strokes. Mode 8 (Auto-Sensing) activates on skin contact and shuts off automatically 1 minute after leaving the skin.
Key Benefits
- 3-level heat (46°C / 42°C / 38°C) induces vasodilation — increases dermal blood flow 3–5x above baseline at the highest level
- Thermophoresis effect: heat temporarily fluidizes stratum corneum lipid matrix — increases active ingredient penetration to dermis
- Cold Full/Half intensity (Modes 4–5) induces vasoconstriction — reduces capillary fluid leakage, decreases morning puffiness accumulation
- Cold reduces post-treatment inflammatory mediator activity — shortens recovery from microcurrent or active ingredient redness
- Pore appearance reduction: vasoconstriction firms surrounding tissue — pores appear visibly smaller after cold application
- Temperature contrast vascular pump: alternating vasodilation and vasoconstriction increases lymphatic and venous waste clearance
- Cold consolidates the firming effect of the full protocol — sealing the treatment results
How It Works
- Step 1 — Mode 1 (Red light + 46°C / 114.8°F + Vibration, 1–2 min): Apply to target area before any other treatment mode or active ingredient. Slow circular or stroking motion. Do not hold stationary. This is the priming step — everything applied or performed after this is more effective. Red light activates collagen synthesis simultaneously. Use Mode 2 (42°C) or Mode 3 (38°C) for sensitive skin.
- Step 2 — Apply active serum: Apply retinol, vitamin C, peptide serum, or hyaluronic acid to heat-primed skin immediately. The 2–3 minute window after heat application represents peak permeability.
- Step 3 — Microcurrent (Mode 6: Violet light + EMS + Vibration, or Mode 7: White light + EMS Strong + Vibration, 3–4 min): Forehead, cheeks, jawline, neck. The heat-primed dermis and elevated blood flow maximize fibroblast ATP response.
- Step 4 — Additional LED (optional, 2–3 min): Mode 2 (Cyan light + 42°C heat) for soothing; Mode 3 (Yellow light + 38°C heat) for brightening — or continue with the red light benefit already delivered in Step 1.
- Step 5 — Mode 4 (Green light + Cold Full intensity) or Mode 5 (Blue light + Cold Half intensity), 1–2 min: Apply to full face and neck after completing treatment modes. Slow gliding motion. This is the sealing step — vasoconstriction consolidates the treatment, reduces any redness, firms tissue, reduces pore appearance. Apply moisturizer or SPF to cold-finished skin.
- Total temperature contrast component: 3–4 minutes (heat + cold). Insert within any full protocol without extending total session time significantly.
Scientific Claims
- Heat at 40–46°C increases dermal blood flow 3–5x above baseline through vasodilation
- Thermophoresis: elevated skin temperature increases stratum corneum permeability — enhances transdermal delivery of active ingredients
- Cold Full/Half intensity (Modes 4–5) induces vasoconstriction — reduces capillary hydrostatic pressure and net fluid filtration into interstitial spaces
- Cryotherapy reduces inflammatory mediator activity — prostaglandins and cytokines — through temperature-dependent enzymatic inhibition
- Temperature contrast (alternating heat and cold) increases lymphatic and venous clearance through the vascular pump effect
- Pore size is not permanently altered by temperature, but pore appearance narrows when surrounding tissue is vasoconstricted and firmly contracted
Device Specifications
- Heat Modes: Mode 1 = Red light + 46°C / 114.8°F · Mode 2 = Cyan light + 42°C / 107.6°F · Mode 3 = Yellow light + 38°C / 100.4°F
- Cold Modes: Mode 4 = Green light + Full intensity · Mode 5 = Blue light + Half intensity
- EMS Modes: Mode 6 = Violet light + EMS · Mode 7 = White light + EMS Strong · both 10–300μA
- Mode 8: Auto-Sensing — activates on skin contact, shuts off 1 min after leaving skin
- IPX0 — not waterproof; apply to dry or product-coated skin only
- Head material: Zinc Alloy — rapid temperature conduction for both heat and cold modes
- Safe for face, neck, décolletage
Safety Information
Heat mode: apply with continuous gliding motion — never hold stationary in one position to avoid localized overheating. Do not use on broken, sunburned, or actively irritated skin. Cold mode: avoid applying directly over the eyes or eyelids; use only over bony areas around the orbital ridge. Do not apply cold to areas with impaired sensation. Both modes are safe for daily use. Do not use immediately before or after applying chemical exfoliants (AHAs/BHAs) — heat increases permeability and may cause over-penetration of acids.
What the Research Says About Heat, Cold, and Skin Physiology
"Cryotherapy produces vasoconstriction in the treated area, reducing local blood flow and inflammatory mediator activity. The subsequent reactive hyperemia following cold removal produces a vascular flush effect that accelerates metabolic waste clearance from the tissue — explaining the skin-brightening and firming effects observed after cold facial application."
"Elevated skin temperature increases the fluidity of the stratum corneum lipid bilayer, reducing its barrier function and significantly increasing the permeability coefficient for topically applied molecules. This thermophoresis effect provides a practical basis for heat pre-treatment before active ingredient application in cosmetic protocols."
Both citations are from peer-reviewed and academic sources. The Lubkowska citation links directly to PubMed. The Benson & Watkinson reference is the standard academic text on transdermal delivery — replace URL with specific edition link if available.
Temperature Therapy Methods: Hot & Cold Device vs Ice Roller vs Warm Towel
| DIY Temperature Methods | Hot & Cold Device (Mode 1 + Modes 4–5) |
| Factor | Warm Towel | Ice Roller / Ice Cube | Hot & Cold Device (Modes 1–3 + Modes 4–5) |
|---|---|---|---|
| Heat temperature | ⚠️ Variable, hard to control | ❌ None | ✅ 3 levels: 46°C / 42°C / 38°C (Modes 1–3) |
| Cold intensity | ❌ None | ⚠️ 0°C — too cold, risk of capillary damage | ✅ Full or Half intensity (Modes 4–5) — adjustable, facial-safe |
| Both in one tool | ❌ No | ❌ No | ✅ Yes — instant mode switch |
| Facial contouring | ❌ Flat application | ⚠️ Basic roller | ✅ Curved zinc alloy head — anatomical fit |
| Microbial hygiene | ⚠️ Towel reuse risk | ⚠️ Ice contamination risk | ✅ Zinc alloy — wipeable |
| Session control | ❌ Cools rapidly | ❌ Melts, inconsistent | ✅ Mode 8 Auto-Sensing (shuts off 1 min after leaving skin) |
| Integration with other modes | ❌ Standalone only | ❌ Standalone only | ✅ Designed as part of 8-mode protocol |
The Full Temperature Contrast Protocol (Heat → Treatment → Cold)
If you want to maximize the effectiveness of your active ingredients and microcurrent protocol while finishing with visibly firmer, less puffy, reduced-pore skin — this is the complete temperature contrast sequence that integrates both heat and cold into your existing routine.
- Active ingredients that seem to plateau in effectiveness
- Post-treatment redness lasting more than 30 minutes
- Visible pores you want to minimize before events or photography
- Morning puffiness that hasn't resolved by the time you start your routine
- Want to maximize ROI on high-quality serums
- Using microcurrent and want to enhance and seal results
Complete protocol (10–14 minutes total): Step 1 — Mode 1 (Red light + 46°C / 114.8°F + Vibration, 1–2 min): Full face and neck. Slow circular strokes. Do not hold stationary. Red light activates collagen synthesis simultaneously. Use Mode 2 (42°C) or Mode 3 (38°C) for sensitive skin. Step 2 — Apply active serum immediately: retinol, peptide, vitamin C, or hyaluronic acid to heat-primed skin. The 2–3 minute window after heat represents peak permeability. Step 3 — Microcurrent (Mode 6: Violet light + EMS + Vibration, or Mode 7: White light + EMS Strong + Vibration, 3–4 min): Forehead, cheeks, jawline, neck. The heat-primed dermis and elevated blood flow maximize fibroblast ATP response. Step 4 — Additional LED (optional, 2–3 min): Mode 2 (Cyan light + 42°C heat) for soothing; Mode 3 (Yellow light + 38°C heat) for brightening — or continue with the red light benefit already delivered in Step 1. Step 5 — Mode 4 (Green light + Cold Full intensity) or Mode 5 (Blue light + Cold Half intensity), 1–2 min: Full face and neck. The sealing step — vasoconstriction consolidates treatment results, reduces redness, firms tissue, reduces pore appearance. Mode 8 Auto-Sensing will shut off the device automatically 1 minute after you lift it from your skin. Apply moisturizer or SPF to cold-finished skin.
Cold-Only Quick Protocol (Pre-Event Skin Firming in 3 Minutes)
If you need rapid pore minimization, inflammation reduction, and temporary skin firming before a meeting, photoshoot, or event — the cold-only quick protocol delivers visible results in 3 minutes without requiring the full treatment sequence.
- Pores appearing enlarged before event or photography
- Residual redness from earlier skincare steps
- Need skin to look its best in under 5 minutes
- Post-workout facial flushing
- Morning puffiness that needs rapid resolution
- Pre-makeup skin prep for better foundation application
On clean, moisturized skin: Mode 4 (Green light + Cold Full intensity) or Mode 5 (Blue light + Cold Half intensity), 2–3 min: Full face — forehead, cheeks, nose, jawline, neck. Slow gliding strokes. Pay extra attention to areas of visible pores (nose, cheeks) and puffiness (under-eye, jawline). The vasoconstriction effect is immediate — pore appearance reduction and tissue firming are visible within 1–2 minutes of application. Mode 8 Auto-Sensing will shut off the device automatically 1 minute after you lift it from your skin. Reactive hyperemia (the mild pinkish glow from vascular rebound after cold) resolves within 5 minutes and leaves skin with improved tone and firmness. Apply makeup or SPF immediately after — cold-firmed skin provides a smoother base for foundation. For maximum effect before photography: cold application 10–15 minutes before shooting, allowing the reactive hyperemia to resolve and the vasoconstriction firming to remain.
Research establishing cryotherapy's physiological mechanisms including vasoconstriction, inflammatory mediator reduction, and reactive hyperemia — the vascular basis for cold therapy's skin-firming and brightening effects in facial applications.
Standard academic reference for transdermal delivery mechanisms — documents the thermophoresis effect whereby elevated skin temperature fluidizes the stratum corneum lipid bilayer, increasing permeability for topically applied molecules and providing the scientific basis for heat pre-treatment before active skincare application.
My Vitamin C Actually Works Now — I Think the Heat Step Is Why
I've been using a high-end vitamin C serum for about 6 months and it was fine but not producing the results I expected from the price point. A friend told me to try warming my skin before applying it. I started using the heat mode for about 90 seconds before my serum and then finishing with the cold mode after my other treatments. Within 2 weeks my skin looked noticeably brighter and the texture improved in a way it hadn't in the previous 6 months. I genuinely think the serum was just sitting on the surface before. The cold finish is also something I didn't expect to like as much as I do — my pores look so much smaller immediately after and it kind of sets everything.
Vitamin C results improved significantly after adding heat pre-treatment — plus visible pore reduction from cold finish
Common Questions About Hot and Cold Therapy for the Face
Should you use hot or cold therapy on your face first?
The correct sequence: warm (Modes 1–3) to relax facial tissue and prepare skin before massage → microcurrent massage strokes (Modes 6–7) → cold (Modes 4–5) to refresh and firm the skin as the finishing step.
Starting with cold constricts the tissue before you've done any massage work, making the routine less comfortable and less effective. Cold is a finishing treatment — it seals and refreshes after the active work is done. After cold mode ends on the ELEVAURE, the built-in cooling fan runs for 30 seconds then stops automatically.
What does heat therapy do for your skin?
First, it helps facial tissue feel more relaxed and receptive before massage strokes — warm skin is more comfortable to massage and responds better to the directional pressure of gua sha strokes.
Second, warm skin absorbs skincare products more readily. Serums, peptides, retinol, and hyaluronic acid applied immediately after a warm massage routine penetrate more effectively than the same products applied to cold, un-massaged skin. Apply your actives in the 2–3 minute window right after the warm phase for best absorption.
Use Mode 3 (Yellow light + 38°C) for sensitive skin, Mode 2 (Cyan light + 42°C) for normal skin, Mode 1 (Red light + 46°C) for maximum warmth. Always keep the device moving — never hold stationary on one spot.
What does cold therapy do for facial skin?
As a finishing step after warm massage, cold is particularly effective for: reducing the appearance of under-eye puffiness, minimizing the look of pores temporarily, reducing any redness from massage, and leaving skin with a visibly tighter, more defined appearance.
Use Mode 5 (Half intensity) if full cold feels too intense — especially useful for sensitive skin or first-time users. After cold mode ends, the device cooling fan runs for 30 seconds then stops automatically — this is normal.
Does heat help skincare products absorb better?
The practical approach: after your warm massage phase (Modes 1–3), apply your serum — vitamin C, peptides, hyaluronic acid, or retinol — to warm skin before it cools. The 2–3 minute window right after the warm phase gives the best absorption. Then continue with moisturizer and SPF as normal.
This works with any warm facial massage. The ELEVAURE's built-in warm modes (38°C / 42°C / 46°C) make it easy to incorporate into an existing skincare routine without a separate facial steamer or hot towel.
How often can you use hot and cold therapy on your face?
For active improvement (firming, depuffing, line softening): 5 sessions per week for the first 8 weeks, then 3–5 sessions per week for maintenance.
The device has built-in auto shut-off: 1 minute in standby, 10 minutes in warm or microcurrent modes. Mode 8 (Auto-Sensing) activates on skin contact and shuts off 1 minute after you lift it away — no timer needed during your daily routine.
For sensitive skin: start with Mode 3 (38°C, lowest heat) and Mode 6 (EMS, lower intensity) and assess skin response before increasing intensity.
Does cold therapy permanently shrink pores?
Regular cold finishing after warm massage can help keep pores consistently looking their smallest as part of a daily routine, and warm massage before applying pore-minimizing serums improves their absorption. But any product or device that claims to permanently shrink pores is overstating what the technology can do.
Is hot and cold therapy safe for sensitive skin?
For sensitive skin: start with Mode 3 (Yellow light + 38°C / 100.4°F) — the lowest heat level. Use Mode 6 (EMS) rather than Mode 7 (EMS Strong) for microcurrent. Use Mode 5 (Blue light + Cold Half intensity) rather than Mode 4 for cooling.
Always keep the device moving with gliding strokes — never hold stationary on one area. Do a patch test on the inner wrist before first full facial use. Discontinue use and consult a healthcare professional if you experience persistent redness, irritation, or discomfort.
Do not use on broken skin, active acne lesions, or sunburned skin. This device is a personal care massage tool, not a medical device.
What is thermophoresis in skincare?
In practical terms for a facial massage routine: when you apply a serum or active ingredient to skin that has just been warmed by a facial massage device, the ingredient penetrates more effectively than if applied to cold skin. This is the basis for applying serums immediately after the warm phase of a hot-and-cold facial routine — not after the cold finishing step.
Note: thermophoresis as a cosmetic claim is not regulated or standardized — the term is used loosely in beauty marketing. The underlying principle (warm skin absorbs products more readily) is well-established; the magnitude of the effect varies by ingredient and formulation.
Heat Opens Your Skin. Cold Seals It. One Device Does Both.
The Elevaure 7-in-1 (8 Modes) Hot & Cold Face & Neck Beauty Device delivers 3-level thermotherapy (Mode 1: 46°C / 114.8°F, Mode 2: 42°C / 107.6°F, Mode 3: 38°C / 100.4°F) and 2-level cryotherapy (Mode 4: Full intensity, Mode 5: Half intensity) — the complete temperature contrast protocol in a single zinc alloy device. Use heat to prime your skin before active ingredients and microcurrent, and cold to seal, firm, and reduce inflammation after treatment. Add temperature to your routine and every other step works better.
Modes 1–3 (Heat: 46°C / 42°C / 38°C) + Modes 4–5 (Cold Full / Half intensity) — temperature contrast in one device
Shop the DeviceRead: Heat vs. Cold vs. Microcurrent — Which Therapy Does What?