Patch testing and declared allergens

In brief

Test any new leave-on product on a small area before you use it on your face or scalp. Apply a small amount to the inside of the forearm or the bend of the elbow twice a day for 7 to 10 days. If there is no redness, itching, swelling or burning, use it as directed. If there is, stop.

How to patch test

1. Choose a small area you can see, such as the inside of the forearm or the bend of the elbow. For a scalp product, a small area behind the ear, near the hairline, is closer to where it will be used.
2. Apply a small amount twice a day for 7 to 10 days, in the same place, and leave it on.
3. Check the area each day. Look for redness, itching, swelling, burning, bumps or a rash.
4. If nothing happens, start using the product as directed.
5. If a reaction appears, rinse the area with water and stop using the product.

Test one new product at a time. If two new products go on at once and a reaction appears, there is no way to know which caused it.

Professionals patch test before a first treatment with any new product, and before any acid treatment, as set out in each protocol. See the sensitive skin barrier protocol for an example.

When to stop and get help

Stop using the product if you see redness that spreads, itching, swelling, burning, blistering or a rash, whether during the patch test or later.

Call emergency services at once if you have swelling of the face, lips, tongue or throat, or any difficulty breathing.

See a doctor or pharmacist if a reaction spreads, blisters, or has not settled within a few days of stopping.

Then tell us what happened through report a reaction. Keep the carton: the lot number and expiry date on it identify the exact product.

Declared allergens and ingredients to check, by formula

A declared fragrance allergen is a fragrance component named individually in the ingredient list. Some markets require specified fragrance allergens to be named this way above a set concentration. More on what they are is on fragrance allergens.

Of the seven NanoSerum formulas, two declare fragrance allergens: Scalp Repair NanoSerum declares Citronellol and Limonene, and Sculpting NanoSerum declares Limonene and Citral.

The table covers the sealed vial set of each formula, and the 30 ml bottle for Scalp Repair. The full declaration for each formula is in its dossier on the evidence hub. How to read one is explained in how to read an INCI list.

Formula notes

Leave-on acids. Brightening NanoSerum contains alpha hydroxy acids. Its sun statement applies:

Sunburn Alert: This product contains an alpha hydroxy acid (AHA) that may increase your skin's sensitivity to the sun and particularly the possibility of sunburn. Use a sunscreen, wear protective clothing, and limit sun exposure while using this product and for a week afterwards.

Why acids and sun exposure go together is in acids and sun sensitivity.

Essential oils. Clarifying NanoSerum contains tea tree leaf oil and rosemary leaf extract, Scalp Repair NanoSerum contains bergamot and geranium oils, and Sculpting NanoSerum contains patchouli, lemon peel, eucalyptus, lemongrass, citronella and peppermint oils. If you have reacted to essential oils or fragranced products before, patch test these first. See tea tree oil.

Salicylic acid. Clarifying and Scalp Repair contain salicylic acid. If a doctor has told you to avoid salicylates or aspirin, ask before using either.

Fragrance. Hyaluronic Skin Repair NanoSerum is fragrance free. Sculpting NanoSerum is scented by its essential oils and declares Limonene and Citral. Free-from statements are made per formula from its own declaration; the table above is the reference for the others.

Related

For routines built around reactive skin, see sensitive skin. The other safety pages are listed on the science hub, including regulatory status.