How to Patch Test *All* Your Beauty Products (And When You Really Should)
Main image – Valbarstudio/Stocksy
If you’re savvy enough to read a product’s instructions before using it, then you’ll probably recognise the term ‘patch test’. It’s something you can do as a little insurance policy for your skin before trying something for the first time.
But what can happen if you don’t patch test? And how do you patch test your skincare, makeup and hair products the right way? I asked dermatologist Dr Hannah Kopelman, hair stylists Michael Douglas and Maria Sotiriou, and makeup artist Ruby Hammer for their expert tips.
Why patch testing in beauty is important
Whether your skin is sensitive or not, most people can be at risk of having a reaction to something new. “I see a lot of patients who experience unexpected reactions to skincare products, often because they didn’t patch test beforehand,” warns Dr Kopelman.
“Patch testing allows you to see how your skin will respond to a product or ingredient in a controlled way, rather than risking a reaction on your entire face or body. This is particularly important for those with sensitive skin, rosacea, or eczema, as their skin is already more reactive”
And it’s not just important for when you’re trying new products either – it helps when using new ingredients too. “I also encourage it when patients want to try new active ingredients, like retinol or exfoliating acids, since these are more likely to cause irritation or dryness if their skin isn’t used to them,” she adds.
Image – Katarinaradovic/Stocksy
“It’s a simple step that can prevent a lot of unnecessary skin issues and help patients feel more confident about their choices.”
How to patch test your skincare
“When I show patients how to patch test, I recommend they apply a small amount of the product to a discreet area of their skin—behind the ear or on the inner forearm works well,” explains Dr Kopelman.
“I usually suggest they use enough product to cover about a one-inch area and leave it on for 24 to 48 hours. If they’re testing something strong, like a retinoid or an exfoliating acid, I tell them to extend the testing period to up to five days, applying daily to see if any delayed reactions occur.”
So what are the signs of a reaction? “I always stress that if they notice redness, itching, or irritation, they should stop immediately and not proceed with using the product on their face,” she says.
How to patch test your haircare
Whilst experts say that products like styling products, shampoos and conditioners don’t require a patch test, if you’ve had a previous reaction to a product- or you have a particularly sensitive skin or scalp- you may want to do it anyway to be on the safe side.
“My advice would be to place a small sample of product on the skin behind the ear, also on the nape of the neck,” explains Sotiriou. “Leave it for 30 minutes, then wipe the product away and check to see if there is any change to the appearance of the skin.”
For home hair colouring though, a skin test is always recommended (even if you’ve used the same product before).
Image – Ohlamourstudio/Stocksy
There are two types of tests to do in home hair colour, according to Douglas. “A skin test to see whether you’d be allergic to the materials in the product, and a patch test which is where you would try a bit of the product on a bit of your hair to get an idea of the colour result,” he explains.
“Patch tests can be quite difficult to do as it’s very hard to get a sense of what the result would be like on the whole head by just doing a small amount of it,” he adds. However, “it’s probably the best indicator of the type of result you’ll get but it does require the use of your imagination.”
So how do you do a skin test? “Mix a tiny amount equal parts of both the developer and the colourant, imagine about 3 ml of each,” Douglas advises. “Mix them together with a cotton bud, apply to the skin behind the ear and leave that to develop for an hour. This should indicate whether the product is safe for you to use or not.”
And if you feel like doing a home hair colour patch test? “You need to mix up 5 ml each of the products [developer and colourant] and apply to a small amount of hair around the back of the head, develop for the full development time and see what that result is like,” he explains. “Then you can decide whether you want to proceed with using the colour or not.”
How to patch test makeup
According to makeup artist Ruby Hammer MBE, patch testing isn’t always required for makeup, “however when someone sits in front of me the first question I ask is ‘are you allergic or sensitive to anything?’ she explains. “
There are specific beauty procedures that require mandatory patch tests as they contain known allergens, however for your everyday makeup the risks are much lower.”
Image – Magdalenam/Stocksy
It pays to be cautious though. “If you know you are sensitive you should patch test all your cosmetics to keep your skin safe from irritation,” she says.
“I would usually test on the wrist or inside of the elbow and do a simple swipe of the makeup and see if there is a reaction. If you are particularly sensitive, I would leave for 24 hours minimum in case of delayed reactions.”
How to patch test gel nail polish
Did you know, some gel nail polishes can be harmful when they come into contact with the skin?
“The issue arises from ingredients like acrylates and methacrylates, which are used in the formulation of gel polishes,” Dr Kopelman says.
Image – Sonjalekovic/Stocksy
“These chemicals can irritate the skin or trigger allergic reactions when they come into direct contact during application. Symptoms may include redness, itching, or even blistering around the nails or on the skin that was exposed.”
So how do you minimise the risk? “It’s crucial to avoid letting the polish touch your skin during application,” she warns.
“Opting for a professional manicure at a reputable salon is generally safer than doing it yourself, as trained nail technicians are skilled at avoiding contact with the skin. Additionally, ensure the salon uses high-quality products and follows proper curing techniques, as improperly cured gel polish can increase the risk of reactions.”
Prefer doing your gel mani from home? “Choosing brands labelled as “toxin-free” or
“hypoallergenic” may help reduce the risk, but it’s not a guarantee. The best approach is to wear gloves during application (leaving the nails exposed) and ensure the polish is fully cured under a UV or LED lamp.”
The takeaway
Patch testing, or skin testing in home hair colouring, is a really sensible idea when you’re using a product or ingredient for the very first time. As Dr Kopelman says, you never know when your skin might react negatively to something.
If a reaction like redness, itching and dryness is going to occur, it’s better to test it elsewhere first on a small, discreet area such as behind the ear or forearm rather than all over your face or scalp.
Book a salon appointment to have gel nail polish professionally applied to minimise the risk of a skin reaction. And if you are going to do a patch or skin test before using anything else, make sure you leave it on for the required amount of time so that you can be confident about applying it properly when the time comes.
Meet the experts
Dr. Hannah Kopelman has completed two clinical fellowships in dermatology – hair loss from Columbia University and skin cancer from Boston University. She is also extremely active on YouTube, Instagram, TikTok and also has a weekly dermatology podcast called Derm Club.
Ruby Hammer MBE is a makeup artist, beauty expert and founder of Ruby Hammer Beauty.
Michael Douglas is a hairdresser and founder of MD London.
Maria Sotiriou is founder of Silke London.
Get Glowing!
