IPL and skin tone: the safety limit every brand buries

IPL fires a broad-spectrum pulse of light. Melanin absorbs it and converts it to heat. In a hair follicle, that heat disrupts the structures that grow hair. That is the entire mechanism.

The limitation is built into the mechanism: the device cannot distinguish melanin in a hair from melanin in skin. It heats whatever absorbs the pulse.

On high-contrast combinations - lighter skin, dark hair - the follicle absorbs far more than the surrounding tissue, and the heat goes where it is wanted. As the melanin content of the skin rises, the surrounding tissue takes a larger share of each pulse. Beyond a point the energy needed to affect the follicle is also enough to injure the skin.

This is not a manufacturing shortcoming that a better handset will solve. It is what happens when you use broad-spectrum light and melanin as your targeting system.

Note the direction of the scale: the risk is not that the device will not work. It is that it will deposit energy in your skin instead of your follicle.

The same mechanism means very light blonde, red, white and gray hair do not respond at all, on any skin tone. Those hairs lack the melanin needed to absorb the pulse. More energy does not help; the target is simply not there.

This matters more with age and it matters enormously on the face and chest, where gray appears first. Nood's compatibility documentation states it plainly; several brands do not, and a buyer discovers it after twelve weeks of sessions.

• Burns. Thermal injury where the skin absorbed energy intended for the follicle.
• Blistering, in more severe cases.
• Post-inflammatory hyperpigmentation. Darker patches following the inflammation, which on deeper skin tones can be prominent and can persist for months or longer - often far longer than the hair would have taken to regrow.
• Hypopigmentation. Lighter patches where pigment-producing cells were damaged. Less common and potentially longer-lasting.

These are not theoretical. They are the reason the ceiling exists, the reason manufacturers publish compatibility charts, and the reason we would rather this page cost us a sale than contribute to one of them.

Some devices read your skin tone and adjust or refuse. Braun's SkinPro 2.0 reads 80 times a second and will not fire at a setting it judges unsuitable. Cyden's SmoothSkin line uses the same lineage. Philips's SmartSkin reads tone and recommends a setting.

Others - including the high-energy Ulike handsets and the Nood - give you intensity levels and a compatibility chart, and rely on you reading it.

1. Pick a small area in the region you intend to treat. Not your forearm if you are treating a bikini line - different skin, different tone.
2. Use the setting you intend to use, or the one the sensor selects there.
3. Fire a few pulses and stop.
4. Wait the manufacturer's stated interval, usually 24 hours. Do not shorten it; delayed reactions are the point of the wait.
5. Check for anything beyond a brief mild flush: persistent redness, swelling, blistering, darkening or lightening. Any of those means stop.
6. Repeat whenever anything changes - a new area, a higher setting, a different device, a tan, a new medication.

• A tan, including a mild one you have not noticed. Tanned skin has more active melanin and absorbs more. Every manufacturer specifies a gap after sun exposure.
• Self-tan. It sits in the stratum corneum and will absorb the pulse. Remove it completely and wait.
• Recent sunburn. Do not treat compromised skin at all.
• Photosensitizing medication. Several common drug classes increase light sensitivity. Your pharmacist will tell you in two minutes.
• Seasonal variation. The skin tone you tested on in February is not the skin tone you have in July.

• Professional Nd:YAG laser. The 1064 nm wavelength penetrates deeper and is absorbed much less by epidermal melanin, which is why it is the clinic standard for deeper skin tones. Compared here.
• Electrolysis. Destroys the follicle with current, so melanin contrast is irrelevant. Works on any skin tone and any hair color, and it is the only method recognized as permanent. Compared here.
• Conventional methods. Unglamorous, entirely safe, and better than a burn that outlasts the hair by a year.

• The sensation is sharp or burning rather than a brief warm snap.
• Redness persists well beyond a short flush.
• You see any blistering, however small.
• The skin darkens or lightens in treated areas over the following days.
• You see a pattern matching the device window.

None of that is a reason to push on at a lower setting the same day. Stop, let the skin recover fully, and reconsider whether the device suits you. If anything blisters or pigment changes, see a clinician - it is worth five minutes of someone's time to avoid something that lasts months.

This page reports what manufacturers and regulators publish. It is not medical advice and we are not clinicians. If you have melasma, a history of post-inflammatory hyperpigmentation, or any doubt about your suitability, that conversation is with a dermatologist and it is worth having before you spend.