So I started a new skin lotion and several days later … a rash develops… how do I know if I have a skin allergy?

Today we will go over allergic reactions – which develop when the body’s immune system recognize that certain substances are harmful and reacts accordingly.

Hypersensitivity reactions

Let’s review: one’s body can develop 4 main types of allergic reactions – also known as “hypersensitivity reactions.” These reactions are your body’s way of helping you, but sometimes too much of a good thing is not always good for you.

Type 1 is what we commonly think of as allergies – where you might eat something like peanuts or get stung by a bee and then immediately develop a life threatening condition called anaphylaxis. Type 2 is seen when your body forms antibodies against your own tissues and Type 3 is when these antibodies form complexes that may clump together to cause havoc on your organs. Type 4 is what we are going to focus on today, it’s the delayed hypersensitivity reaction of allergic contact dermatitis.

Anaphylaxis can be life threatening, immediate

But before we can even talk about skin allergies, it’s easier to compare it to environmental allergies. Allergies from the environment, foods, medications, etc may cause an immediate reaction which include symptoms such as hives (itchy pink raised bumps), itchy eyes, runny nose, and in severe cases, swelling of your face and throat. This may lead to difficulty breathing and can be life threatening. To identify allergens to pollen, mold, pet dander, dust mites, foods, or medications, a skin prick test or puncture or scratch test is performed. Although it can be performed anywhere on the body, it is commonly done on the arms or back given the larger surface area (more space to do more tests). Blood tests can also help identify these allergens.

Allergic contact dermatitis is itchy and slow

On the other hand, allergic contact dermatitis (ACD) falls under type 4 hypersensitivity reactions. It is slow and delayed. The body first has to recognize that the allergen touching your skin is harmful, then it tells it’s soldiers to start fighting and days later, you get an itchy red rash that looks very similar to eczema. The problem is … it takes a detective to figure out what the allergen was in the first place. The most common type of ACD is nickel, and presents as itchy ear lobes days after you wear those pesky earrings that you get from a mall stand. But there are so many other causes of ACD such as fragrance or even chemicals you have never heard of… phenoxyethanol, methylchloroisothiazolinone, etc etc.

To test for ACD – a skin patch test is done. Normally, we place a series of stickers each containing an allergen on the patient’s back, then remove them 2-3 days later, and then do a final reading 2-3 days after that. If there is a reaction – an itchy red rash, then this is a positive test. The issue is, you cannot get your back wet for about 5-7 days, aka no showering or exercising. There are a few patch test series, the most comprehensive one is the American Contact Dermatitis Society 80 allergens panel.

As annoying as this test is, it’s even more annoying to have a rash that never goes away. There are so many added ingredients in skin care products and the list is ever-changing so it’s helpful to have a test to figure out what allergen is causing a pesky rash on your body.

Thus, if you ever get new itchy rash and you have never had itchy skin before, think possibly, allergic contact dermatitis and find a dermatologist to help you do the detective work to find your trigger.