How to Patch Test Skincare (UK Guide to Avoiding Reactions)

November 25, 2025

If you only read one bit, make it this:

To patch test a new skincare product at home in the UK:

Choose a small area – usually the inner forearm or behind the ear.
Apply a pea-sized amount of product to clean, dry skin.
Leave it on for 24–48 hours (re-apply once a day for strong actives like retinol/acids).
Watch for reactions during and after: redness, burning, itching, bumps, swelling, or blisters = do not use on your face/body.
If you get a severe reaction (swelling around eyes/mouth, spreading rash, trouble breathing), rinse off and seek urgent medical advice via NHS 111 or A&E.

That’s the short version. Now here’s a Google-friendly, in-depth guide.

Why patch test skincare in the UK?

Even though cosmetic products sold in the UK have to meet strict safety rules and be assessed as safe for normal use, individuals can still react to specific ingredients.GOV.UK+1

Common issues include:

Red, itchy rash (contact dermatitis)
Stinging, burning or tightness
Flare-ups of eczema or rosacea

The NHS uses patch testing in dermatology clinics to identify delayed skin allergies to substances like preservatives, fragrances and metals. At home, a simple patch test before trying new skincare is a practical way to lower your risk of a reaction.

Order our Vitamin C serum here

Quick answer: How to patch test a new skincare product

Here’s a clear, step-by-step method designed for UK consumers and suitable for most leave-on products (serums, moisturisers, eye creams, oils):

Step 1: Pick the right test area

Good options:

Inner forearm – easy to see and check
Behind the ear (on the neck just below the ear) – skin here is more similar to facial skin

Avoid:

Broken, irritated, sunburnt or shaved skin
Areas with active eczema flare-ups (speak to your GP/dermatologist first)

Step 2: Clean and dry the skin

Wash the area with a gentle, fragrance-free cleanser or just lukewarm water.
Pat dry with a clean towel.
Don’t apply other skincare or perfume on that spot.

Step 3: Apply a small amount of product

Use a pea-sized amount (or 1–2 drops for a serum).
Smooth it onto an area about the size of a £1 coin.
For leave-on products, do not rinse it off unless you react.

For very strong actives (e.g. high-strength retinol, AHA/BHA peels), use even less and stay away from sensitive areas like eyelids or corners of the nose.

Step 4: Decide whether to cover it

You can:

Leave it uncovered – easiest and fine for most products
Or cover lightly with a small plaster if it’s likely to rub off (avoid if plasters irritate your skin)

Step 5: Monitor for 24–48 hours

Reactions can be immediate or delayed.Allergy UK | National Charity+1

Check:

After 15–30 minutes, look for intense burning, stinging, or bright redness
After a few hours, check for new redness, itching, bumps or hives
At 24 and 48 hours – look for delayed reactions: dry, rough, itchy, scaly or blistered skin

If you’re testing strong actives (retinol, exfoliating acids, strong vitamin C):

Reapply once a day for 2–3 days to the same spot
Keep checking for delayed irritation or dryness

Step 6: How to read the results

Generally OK to use (start slowly on the face) if:

No redness, itching or burning
Maybe very mild, short-lived tingling that settles within 10–15 minutes (common with some acids/vitamin C)

Do not use if:

Redness that persists
Itching, stinging or burning
Swelling, raised bumps or hives
Blisters, oozing or broken skin

If you get a reaction, rinse gently with lukewarm water, stop using the product and avoid similar products (e.g. those with the same fragrance or preservative).

What a normal vs a bad reaction looks like

Normal / expected (often with actives)
Mild warmth or tingling that settles quickly
Slight dryness over time (especially with retinol/acid products – often managed with a good moisturiser)

Concerning reactions

Stop using the product and do not apply it to your face if you notice:

Bright, well-defined redness
Itching that makes you want to scratch
Burning or pain
Small bumps, hives or a rash
Swelling around the eyes or lips

Emergency signs – get urgent help

Call NHS 111 or seek urgent medical care if you notice:

Swelling of the face, tongue or throat

Difficulty breathing or swallowing

Dizziness, feeling faint or very unwell

These can be signs of a serious allergic reaction and need urgent assessment.

At-home patch testing vs clinical patch testing (UK)

It’s useful to understand the difference:

At-home patch test (what you’re doing here)

You test one product (e.g. a serum) on a small patch of your own skin
Purpose: to see if that product irritates your skin
Good for: new skincare, hair dye, body lotions, deodorants, etc.Green People+1

Clinical patch testing (NHS / dermatologist)

The NHS and UK dermatology services use formal patch testing when they suspect contact allergy (e.g. you keep getting an unexplained rash). Tiny amounts of many known allergens (metals, preservatives, fragrances, rubbers) are applied to your back for a few days and checked for reactions.

Done in hospital or specialist clinics
Requires referral from your GP in most cases
..Helps identify which exact ingredient or allergen is causing problems

If you keep reacting to lots of products despite careful patch testing at home, ask your GP about a referral for formal patch testing.

Extra tips for UK shoppers

1. Check the label properly

In the UK, cosmetic products must:

List ingredients (INCI list)
Include the “period after opening” symbol (e.g. 6M, 12M)
Show a UK-based Responsible Person address or details, meaning someone is legally responsible for safety in Great Britain.

Always:

Avoid using products past their PAO date (e.g. still using a 6M product 2 years later)
Be cautious with products that smell “off”, have separated, changed colour or texture

2. If you suspect a serious adverse reaction

For medicine-type products and some borderline products, the MHRA Yellow Card scheme collects reports of suspected adverse reactions in the UK.

If a product caused a severe or unusual reaction, you can discuss reporting it with your GP, pharmacist or via the Yellow Card website.

Who should be especially careful with patch testing?

Sensitive or reactive skin
Eczema, psoriasis or rosacea
History of allergies or contact dermatitis (especially to fragrance, preservatives, metals)
People using prescription skincare (e.g. topical steroids, tretinoin – follow your prescriber’s advice)

If you’re under the care of a dermatologist, follow their instructions first, especially about where and how to test products.

FAQ: Patch testing skincare (UK)

How long should I patch test skincare?

Aim for 24–48 hours, checking several times. For strong actives like retinol or acids, it’s sensible to test for 2–3 days, re-applying once a day to the same spot and watching for delayed irritation.

Do I really have to patch test every product?

You don’t have to, but it’s strongly recommended for:

New brands you’ve never tried
Products with fragrance, essential oils or strong actives
Anything going near eyes, neck or broken skin

If your skin is quite resilient, you might only patch test “riskier” products (retinol, acids, peels, strong vitamin C). If you’re sensitive, it’s worth patch testing everything.

Where’s the best place to patch test?

Inner forearm – easiest option for most people
Behind the ear / along the jawline – more similar to facial skin, useful for facial products

Avoid thin, delicate skin around the eyes and lips for testing.

Do I need to patch test hair dye?

Yes – especially permanent and dark dyes. Many UK salons already insist on a patch test 24–48 hours before colouring.

At home, follow the manufacturer’s instructions in full. If you get any reaction on the patch test (itching, redness, burning), do not proceed with the full treatment.

When should I skip DIY testing and speak to a professional?

Go straight to your GP, pharmacist or NHS 111 if:

You’ve had a serious reaction to skincare, hair dye or cosmetics
Your rash keeps coming back despite avoiding a product
The reaction spreads quickly or affects your face/eyes/genitals
You feel unwell, have a fever or feel generally “off” alongside the rash

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