How to Patch Test an IPL Device: A Step-by-Step Guide to Safer Hair Removal

There exists a unique form of optimism associated with the experience of unboxing one’s newly acquired at-home device. One had already made their necessary enquiries and looked up some reviews, and they were ready to start. Then you see the instruction that says, 'Do a patch test before anything else.'

It is tempting to skip it. Your skin looks fine, you are not especially sensitive, and you have used plenty of skincare products without issue. But a patch test for an IPL device is a different thing entirely from testing a new moisturiser. The energy involved is not chemical — it is light-based, and your skin's response to it depends on variables that are not always visible or predictable.

This article clarifies what an IPL patch test really means, why it deserves to be done right, and how you can perform it – regardless of whether you use the Ulike Air 3 or some other device. This information is not meant to discourage you – most people complete the procedure without any problems and go straight to the first treatment. However, knowing what you should expect and why helps make things a lot clearer

The phrase "patch test" gets used across a lot of different contexts — from hair dye to false lash adhesive — so it is worth being clear about what it means specifically for IPL.

An IPL patch test is a controlled trial of the device on a small area of skin, carried out before you begin treating any larger or more visible body part. You apply one or a few flashes of light to a discreet spot, at the lowest intensity setting, and then observe how your skin responds over the following 24 to 48 hours.

The purpose is not to test for an allergic reaction in the way you would with a skincare ingredient. It is to assess how your skin responds to concentrated pulsed light energy in general, and specifically at the intensity level you intend to use. Some individuals will experience no response whatsoever from their skin, while others may notice some degree of redness or sensitivity that fades away after a couple of hours. However, there are a few cases where one’s skin will not be able to tolerate the environment.

The purpose of doing the skin test is to determine whether that particular ingredient can cause irritation or allergic reactions on your skin. This reaction can only happen because of the chemistry within your skin.

In the case of IPL, everything changes. IPL is done using high-energy light pulses, which are directed at the hair follicles through melanin, where the light pulses convert into heat. Therefore, the light pulses work based on melanin. This is why not only the skin tone but also the colour of hair becomes relevant.

As it involves a heating process, it means that your reaction is not dependent on how sensitive you are towards a particular ingredient, but on how suitable it is for your skin tone and hair.

The short answer is that skin's response to light-based energy is individual, and you cannot reliably predict it in advance just by looking at your skin.

Most people know that IPL is not suitable for all skin tones — and that is because of how IPL technology works. IPL targets melanin, the pigment in your hair. The contrast between the melanin in the hair and the melanin in the surrounding skin determines how selectively the device can deliver its energy. On lighter skin with darker hair, that contrast is high, and the device can work efficiently. On darker skin, the contrast is lower, and the surrounding skin absorbs more of the light energy — which increases the risk of discomfort, redness, or in some cases, changes in pigmentation.

But skin tone is only one part of the picture. The state of the skin can also be a determining factor on a particular day. When skin is lightly sunburnt, newly bronzed, or sensitised by a recent waxing or shaving, it will have a different reaction than when skin is in its normal state. Changes in hormone levels change skin sensitivity. Some medications increase photosensitivity in the skin. This does not make the skin unique; rather, it makes it what it is – living tissue that is dynamic.

A patch test accounts for all of this. It gives you a small, low-stakes data point from your own body, which is more reliable than any general guidance.

Most of the risks associated with skipping a patch test are not dramatic. For the majority of people, the worst that would happen is some temporary redness or irritation in the treated area. 

But in some cases — particularly where skin tone, medication, or recent sun exposure has not been accounted for — the consequences can include burns, blistering, or post-inflammatory hyperpigmentation, where the skin darkens in response to irritation.

These are not common outcomes, but they are avoidable ones. A patch test takes around ten minutes and requires a 48-hour wait. That is a reasonable exchange for confidence that your skin and the device are going to work well together.

Pick an area that closely resembles the skin you plan to treat, in terms of tone and thickness. If you intend to use the device on your legs, a good test site is the inner forearm or inner calf — areas that are usually less sun-exposed and have relatively thin skin. If you are planning to treat your underarms, the inner arm near the armpit is a reasonable proxy.

Don’t conduct a patch test on:

• The face, neck, or any other thin/fragile-skin area (first-time users should avoid this)

• Skin with any mole, freckle, or even visible veins

• Skin that has open wounds or rashes

• Areas with any tattoo or that are much darker or lighter in skin tone

Always begin at the lowest intensity setting your device offers, regardless of your skin tone, hair colour, or how confident you feel. The patch test is not the moment to find your optimal setting — it is the moment to confirm your skin's baseline tolerance.

If the device has a skin tone sensor, engage it as you would for a normal session. The Ulike Air 3, for example, uses an automatic skin tone detection function that adjusts the recommended intensity level accordingly. This is a useful safeguard, but it does not replace the patch test — it informs which intensity range is appropriate to test within.

Before you begin: Have the patch testing site shaved 24 hours before performing the test. Make sure that no waxing, threading, or chemical hair removal creams are used on the site. The device targets hair beneath the skin's surface — the follicle — and shaving leaves that in place while removing surface hair that would otherwise absorb energy inefficiently and cause unnecessary discomfort.

On the day of the test:

• Clean the region gently and allow it to dry completely before applying any moisturisers or suntan lotion to the previously tested area.

• Wear the goggles provided along with your device. This is not optional — the light emitted during IPL is intense enough to be damaging to the eyes without protection.

• Place the device's flash window flat against the skin on your chosen test site. Make sure there is full contact with the skin.

• Select the lowest intensity setting

• Press the flash button once to produce one flash of light.

• Now shift the apparatus by a few millimetres and repeat the process to produce one or two additional flashes of light, thereby illuminating a small testing region.

• The diameter of a coin of about 50 pence is sufficient.

• Record the exact time, intensity level used, and any sensations felt. Any sensation felt should be minimal, usually just a warm sensation or a slight snap-like sensation. Pain sensations are not normal

After flashing: No active skincare treatments, such as retinoids, AHAs, or other similar ingredients, should be used on the testing area. A fragrance-free moisturiser may be applied to dry or irritated skin.

Now wait. The 48-hour observation window starts from the moment of the last flash.

This is the part most people underestimate. The patch test is not just about what happens in the first few minutes — the 24 to 48 hours that follow are where the meaningful information is gathered.

Re-inspect the test site intermittently; once after an hour of the test, once the next morning, then once again at 48 hours. The criteria will differ somewhat at each of these stages.

Within the first hour, some slight reddening of the treatment site, along with a slight warming sensation, is perfectly natural. The skin has reacted to the light energy absorbed by it, and this will subside in the coming hours.

By 24 hours, all signs of inflammation should be greatly reduced, if not entirely gone. There should be slight sensitivity on the treated site compared to the rest of the skin, but no signs of anger or discomfort.

By 48 hours, the skin should be looking and feeling just as good as ever. Should this be the case, without exhibiting any adverse effects discussed below, you should feel confident proceeding with your first treatment session.

In case any of the above is observed, then a full session should not be carried out. It is best to allow your skin enough time to rest before considering lowering the intensity of IPL treatments in future or using any other treatment that may suit you.

If any reaction is severe, involves broken skin, or does not resolve within a few days, it is worth seeking medical advice rather than waiting to see whether it settles. This is particularly relevant for anyone with conditions that affect skin healing, or who is on medication that may have contributed to the reaction.

A patch test only gives you useful information if it is carried out properly. These are the most frequent mistakes, and why they matter.

Testing on a completely different body area from the one you plan to treat. Skin thickness and tone varies considerably across the body. Testing your inner forearm and then treating your face tells you relatively little about how facial skin will respond. Try to match the test site to the intended treatment area as closely as possible.

Using a higher intensity setting than necessary. The patch test is not the moment to find your optimal setting. Start low. If the test goes well, you can incrementally increase the intensity over subsequent sessions.

Not waiting the full 48 hours. It is understandable to check the area after a few hours and conclude that everything is fine. But some responses develop more slowly — particularly pigmentation changes, which may not be apparent until 24 hours or later. Patience here is not excessive caution; it is the whole point of the exercise.

Testing immediately after sun exposure. A darker complexion will mean that your skin is more sensitive to light. You cannot get an idea of how your skin normally reacts if you conduct a patch test when your skin has been tanned by the sun.

Assuming no pain means no reaction. Certain reactions, including changes in pigmentation, do not cause any sensations of pain. The fact that you did not feel any discomfort during your patch testing is positive, although it cannot substitute for a 48-hour visual evaluation.

Skipping the shave beforehand. Using IPL on unshaved skin causes the surface hair to absorb the light energy and burn, which is uncomfortable and entirely unhelpful. Shave 24 hours before.

IPL is suitable for a wide range of people, but there are groups for whom the patch test is particularly important, and some for whom IPL may not be appropriate at all. This section is not intended to put anyone off — it is intended to help people make an informed decision.

Just because you have skin that flushes easily, reacts poorly to products, or is generally more red than the average person does not mean you can’t use IPL. You just need to be extra careful when performing the patch test, starting with the lowest settings possible.

Those suffering from rosacea and other skin diseases like eczema or psoriasis that have an impact on the skin barrier function should first consult their dermatologists before making use of any of these lights. This is because their skins might behave unpredictably when exposed to light and heat.

The Fitzpatrick classification of skin colour is a method used by dermatologists that determines the type of reaction of your skin towards exposure to sunlight. It ranges from Type I, where your skin is very light, always gets sunburnt, and doesn’t tan at all, to Type VI, where your skin is very dark with no possibility of being sunburnt.

Most consumer-level IPLs are intended for people with Fitzpatrick types I to IV. Skin with types V and VI skin, i.e., medium and dark brown and black, respectively, contains higher levels of melanin in its skin than in its hair.

For people with dark skin, it is crucial to determine what the exact Fitzpatrick scale range is for the machine before anything else. In fact, some modern machines, even newer models of IPL machines, have been created taking into account wider skin tone options; however, there are exceptions here, and a patch test is mandatory.

In case of uncertainty about whether IPL will work well on your skin tone, consulting a dermatologist or any professional aesthetic doctor who works with darker skin types is the best thing to do.

Several other factors can affect how skin responds to IPL, even in people who have used devices without issue before:

Medications. Some of the everyday medications can even cause your skin to be more sensitive to the sun, such as some antibiotics, some acne medications using retinoids (ingested or applied to the skin), various antidepressants and even certain blood pressure medications. It is therefore always prudent to make sure that you verify whether or not the type of food that you are currently taking can make you hypersensitive to the light before you end up trying any form of light treatment.

Pregnancy and hormonal changes. Skin can become more reactive during pregnancy, and there is insufficient evidence on the safety of IPL during pregnancy to recommend it. Many practitioners advise against its use as a precaution. Hormonal contraceptives and the menstrual cycle can also influence skin sensitivity, though to a lesser degree.

Recent cosmetic treatments. When you recently had a chemical peel, laser treatment, or microneedling, then your skin barrier will require time to restore before IPL can be used in the same location. The common rule of thumb is to wait a minimum of four to six weeks, but recovery times are different among individuals.

Tattooed or very darkly pigmented areas. The IPL should not be applied directly to tattoos because the pigment found in the tattoo ink can absorb a great deal of energy from the treatment and will likely result in serious burns.

This article is intended for informational purposes and does not constitute medical advice. If you have a skin condition, are taking prescription medication, or are uncertain whether IPL is appropriate for you, please speak to a GP or dermatologist before use.