Patch Testing Guide


Have you ever tried out a new product and your face went fully red? Have you ever tried out a new product and developed bumps all over your face from it? We all are constantly trying out new products or new routines and sometimes things don’t go as planned or as we hoped for. There is a way to minimize this risk/possibility from happening though! TEST PATCH! Testing patching is quite simple, however the explanation on why I do it and why I recommend all my clients to do it as well is vital.

The first reason I do it, I recommend my clients do it and everyone else to do it is because you never know what you’re allergic to in skincare or makeup (yes, you should test patch makeup products being applied all over your face too). Allergic reactions from topically applied products usually results in allergic contact dermatitis, which is a red (sometimes itchy) bumpy rash. It could also be dry and cracked skin and in severe cases, painful blisters. Although, blisters are rarely caused from cosmetics. This is often confused with an acne breakout, but it is very different. Pimples take a long time to develop, if you are receiving a reaction instantly or 24-48 hours later after using, it is likely allergic contact dermatitis. If this happens, what should you do? If it is instant, I would advise rinsing your face with water for 30 seconds to make sure the product is completely off. If the reaction is very painful, making you lose sleep, too embarrassing, etc, seek medical assistance. In most cases, allergic contact dermatitis is minimal and goes away within a couple of weeks. But, this is why we would limit the area we are testing out to make sure it is not all over your face.

Mild Irritant Contact Dermatitis
Allergic Contact Dermatitis: Hair Dye (Photo provided to me by: Dr. Ryan Riahi)
Severe Allergic Contact Dermatitis (NOT CAUSED FROM COSMETICS)

The second reason we do it is because sometimes we don't realize that ingredients in products do not play well with other ingredients and may cause another reaction that is also contact dermatitis, however it is called irritant contact dermatitis. Simply put, this reaction isn't from you being allergic to the product(s), it's just something in it has damaged the skins' barrier. This is commonly just referred to as a "compromised skin barrier" but in reality, it is a version of contact dermatitis. When you use harsh products that contain drying alcohols, harsh surfactants, over-exfoliation, sun exposure, etc. it can damage your protective layer (the skin barrier) and thus create an unpleasant reaction. Symptoms can include: redness, dryness/tightness, flaking/peeling, stinging or burning when applying other products, increased breakouts. This is a bit trickier to spot because it could happen instantly or after long exposures, however the test match is still something you can follow and you can look out for the symptoms as well.

So, now we know what are the types of contact dermatitis, and we can see that the reactions can be very unpleasant and uncomfortable, we can talk about HOW to test patch effectively.

Thankfully, it's very simple and easy to do. Apply a thin layer of product to a clear area of skin -- by this I mean: no breakout, no redness, and has not had any other products applied to it. My personal preference is on the lower cheek/jaw area or on my neck. Apply it in roughly a 1" x 1" square (no, you don't need a ruler and it doesn't need to be exact or perfect) and do routine check-ins (if possible) every hour to 2 hours. If you are doing this at nighttime, apply the new product(s) and go to sleep. You can also do it on your wrist or cubital area (that's your inner elbow crease). I like to do this two days in a row before I go all over my face with it.

If nothing negative happens the first day, on the second day, I do my routine as normal and then apply the new product the exact same way. This will ensure that the current routine won't cause any irritant contact dermatitis. Sometimes there are ingredients that do not play well together, or they are just too harsh to be combined on your skin. A perfect example: retinoids and AHAs. Although you CAN use products that contain a retinoid and an AHA, and there are studies that did use specifically tretinoin (0.025%) + 12% glycolic acid and showed significant improvements to the skin... HOWEVER, that does not mean you should be doing that because it is 1) overkill and 2) increasing your risks of irritant contact dermatitis. If nothing negative happens on the second day, on the third day, I will apply it all over my face and start including the product regularly into my routine. Personally, I have never followed this guide and then received a reaction down the road. Be mindful that whenever you introduce a new active or a new product to your routine, you may experience a "purge" phase. Maybe in a future blog post I will go over the infamous "purging phase" if people are interested in it! Stay safe!

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