Home remedies or top beauty brands can take care of your skin problems like dryness and acne. But using a kitchen ingredient like lemon or honey or trying out products with preservatives, perfumes or essential oils involves the risk of allergic reactions. That is why you should do a patch test before experimenting with skin care products. Patch testing involves taking a small amount of a product and applying it to the skin then leaving it on to see if there is any reaction. Read on to know how to do a patch test for skin care products.

What is a patch test?

A patch test requires you to apply a small quantity of a substance or product onto the skin, followed by observation to detect any potential reactions. A patch test refers to a diagnostic test that can be used to determine whether specific products result in skin irritation or an allergic reaction, says dermatologist Dr Vinitha Varghese Panicker. The advantage is you can use it on a small area and see for sensitivity before applying the product on large areas.

What are the skin care ingredients you can be allergic to?

Skin care products may contain different ingredients, and some of them may irritate your skin. Here are some such ingredients that are likely to cause a reaction:

• Propylene glycol, a common emulsifier found in skin creams and lotions.
• Linalool, limonene, and citronellol are common fragrance components in moisturisers.
• Coal tar dyes, or synthetic organic dyes derived from petroleum or dyes from herbal sources like indigo dye, and the chemical paraphenylenediamine (PPD), found in permanent hair dyes.

These ingredients may lead to Allergic Contact Dermatitis, a type of skin reaction that occurs when the skin comes into contact with a substance to which a person is allergic. It results in redness, itching or swelling, says Dr Panicker.

Skin patch test in a clinic

Patch testing can be done in a clinic by using special kits to apply the product in question to the skin. The primary difference between at-home patch testing and professional patch testing is that the DIY version can determine if you are sensitive to a product. But it doesn’t tell you if it is an allergy or an irritation, says the expert. You don’t even get to know which ingredient you are specifically reacting to.

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Professional patch testing involves the application of adhesive patches to a patient’s back. Every patch has a single active like dyes and fragrances, which are commonly associated with an allergic reaction. So, this will help in identifying the exact ingredient to which the patient is actually allergic to. The patches are left on for two days after which patients are asked to return for reading. The patches are then removed, and dermatologists look for reactions like redness.

How to do a patch test at home?

You can perform a patch test at home to trial a skin care product before fully incorporating it into your routine. To perform an at-home patch test, follow these steps:

1. Clean your skin

Start by cleaning the area of skin where you intend to apply the product using your regular cleanser. Ensure the skin is free from any dirt, oil, or residue. After cleaning the area, dry it gently with a towel.

2. Apply small amount of the product

Apply a small amount, approximately half the size of a pea, of the skin care product directly in front of your ear. This location allows for easy monitoring and observation of any potential reactions that may occur. Apply the product evenly and avoid spreading it beyond the designated test area.

3. Monitor the skin

Keep an eye on this area of skin for a day. If you notice redness, itching, or irritation in 24 hours then wash the area with a cleanser that is gentle on the skin. Opt for a fragrance-free one, as it is less likely to irritate the skin, suggests the expert.

4. Do a second round of patch testing

If your skin shows no reactions, the product can be used. If there is mild redness and you want to try the product again, a second round of patch testing can be done. The product can be layered with a moisturiser to see if it is better tolerated that way.

If you notice redness or blistering on the area then you are allergic to the product, and you should avoid it.