A Guide to Patch Testing Products in Contact with Skin

Finding the right product to suit your sensitive skin is crucial in order to avoid a reaction that amplifies rather than soothes skin irritation. This guide will help you understand how to test a product in contact with your skin, to check for any reaction. 

What is Patch Testing?

Firstly, it is important to understand patch testing and how it will help you. The irritating and itchy skin reaction that most people experience after using a product that has ingredients that do not agree with your skin is commonly called “contact dermatitis” by clinicians. Patch testing is the main investigation that is used in clinics to understand whether an allergen causes contact dermatitis or skin irritation [1].

The regulations of patch-testing products are different in countries around the world, therefore it may be necessary to read these regulations, especially if you are patch-testing products on people other than yourselves [1].

Patch testing is important in identifying critical allergens that may be present in a certain product and cause contact dermatitis [2]. It is also important to understand some cases of skin reactions are more severe than others and it may be important to consult a dermatologist for advice before testing a product. 

How to perform a patch test?

The following steps are recommended by The American Dermatological Association in patch testing skin care products. This is a guide to test common day-to-day products such as bar soap, shower gels, shampoos, liquid soap, and laundry powders

  • Apply the product twice daily on the skin surface for 7-10 days in an area where it won't easily rub off or wash off. Use a small amount roughly the size of a coin. Surfaces such as the underside of arms or elbow bends are good locations for testing. 
  • Apply the product for the length it would normally stay on before washing or rubbing off. For example: in the case of soap the product is usually washed off after 2 to 3 minutes. 
  • Observe the skin for 10 days for signs of irritation. Skin reactions such as redness, itchiness or swollen skin are common signs of skin irritation. If you do not see any of these signs in 10 days, the product is unlikely to give an irritation. 
  • Some products may cause a temporary reaction. Keep in mind that if irritation disappears after a few days, it is unlikely due to allergic reaction, hence it is important to test a product for at least 7-10 days. 
  • If you develop a skin reaction, gently wash off the product and do not use it again. Applying a cold compress or petroleum jelly may help relieve the irritation. If the reaction is quite severe and does not relieve with cold compress or petroleum jelly, you may need to see a dermatologist to help with your symptoms. 

  • How to understand which ingredient is causing the skin reaction?

    Most of the mass-produced products have a similar range of ingredients in their soaps, shower gels or laundry powders. However, it is very difficult to pinpoint a particular ingredient that may be causing the reaction at home. You may need a “medical patch testing” conducted by a professional to identify the culprit allergen, especially if your skin reaction is quite severe.  After undergoing a medical patch test and the culprit ingredient is identified, you can avoid all products that contain this ingredient. Visit the British Association of Dermatologists for more information on Medical Patch Testing. 

    Determining whether laundry detergent is the cause of skin reaction.

    Unlike products such as soap and shower gels which are created for direct contact with skin, laundry detergents come into indirect contact with skin through your clothes. Some clues that laundry detergent is the cause of a skin reaction are as follows.

    • Rash on side of your face if you are side sleeper. This may be due to laundry detergent on sheets and pillows.
    • Widespread rash on chest and arms above elbows. This may give you a clue if you wore a T-Shirt after washing it.
    • Always ask yourself the question if you have changed your laundry detergent recently?
    • Often the skin reaction is in areas covered by clothing. 
    • Use the laundry detergent for at least 7-10 days before deciding whether it is the culprit as skin reactions may be caused due to several reasons. 

    If you are allergic to the detergent, stop using the detergent. Try changing your detergent to dye-free or allergen free products as it may be possible that you have sensitive skin. If the reaction is quite severe with red flaky skin or hives consult a dermatologist as you may need some anti-allergy treatment. 


    In brief, patch testing is a good practice especially if you have a history of skin allergies. In a household with children, it is good practice to test skin products before using it, especially on children as often skin allergies are hereditary and may be passed down to your children. Patch testing products can save you time and money as products with similar ingredients can be avoided and a product that is suitable to you can be used stress-free. However, it is also important to understand that not all allergens can be identified at home and some times you may need to seek professional help.

    Back to blog

    Article Authored by:

    Dr Ismail Mohammed

    Bachelor or Medicine & Bachelor of Surgery (M.B.B.S), Masters of Research in cardiovascular health and Disease.

    Dr Ismail Mohammed is a medical practitioner and researcher in Manchester, UK. He has 5 years plus of clinical and research experience focussing on innovative and analytical aspects of medical advancement for the future.

    Collapsible content


    1. Foti C, Bonamonte D, Filoni A, Angelini G. Patch Testing. Clinical Contact Dermatitis: A Practical Approach. 2021:499-527. 

    2.Mawhirt SL, Fonacier L. Patch testing and the evaluation of contact allergy. Allergic and Immunologic Diseases. Elsevier; 2022:511-541.