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If you are experiencing itchy or irritated skin, you may be experiencing a skin allergy, and skin allergy patch testing can help identify the cause. A skin allergy patch test is a contact allergy testing procedure designed to diagnose the specific allergen or irritant which is causing your skin allergy. Whether you come into contact with the allergen through touch, inhalation, or digestion, proper allergy testing will identify the cause and help form a treatment plan to avoid future exposure to the allergan. Skin allergy patch testing is primarily used to identify those individuals who are experiencing allergic contact dermatitis, which causes red, inflamed skin on the affected area.

Skin allergy patch testing is typically completed in order to better diagnose an allergic reaction in the skin, and test results are particularly useful for distinguishing between atopic dermatitis (eczema) versus an allergic or contact dermatitis. Board-certified dermatologist Dr. Michele Green is experienced at skin allergy patch testing and is here to help resolve your skin allergy symptoms.

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Patch testing

Patch testing is typically completed over the course of four days, as some reactions take multiple days to develop on the skin.

The process is rather straightforward: a patch test applies the allergens to the skin with specific patches, secured by hypoallergenic tape, that are worn on the upper back for a period of 48 hours. After this 48-hour period, the patches are removed so that Dr. Green can note any positive reactions within the test area and the degree of the allergic reaction. If there is a positive patch test, there will be skin irritation where the patch was placed, indicating a potential allergic reaction. Patients return in an additional 48 hours after the patches are removed to identify and delayed allergic reactions on the skin.

If there is a positive test, the reaction on the skin can range from red and itchy (mild positive) to hives, burning, and either blisters or ulcers (strong positive). A strong positive is highly indicative of an allergy, but multiple strong positives can sometimes lead to a widespread reaction, which can make it difficult to discern the specific allergen. After patch testing is completed, a topical steroid can be used to easily relieve the positive test symptoms.


For patch testing, around 20 to 30 substances will be tested in order to detect an allergy. The typical allergens that are tested in a patch test represent more common allergens, and often will include materials such as metals (nickel), leather, rubber, fragrance, formaldehyde, cosmetics, and hair dyes. Though typically patch testing is completed with around 28 substances, additional allergens may also be tested, primarily taken from the North American Series of Allergens (which includes up to 70 allergen patches).

More specific allergen patches will be applied depending upon your medical history and specific symptoms. Oftentimes a product or material that has been used for years can become an allergen, so it’s important to note any detergents, soaps, skin care items or household products that you have used for years as well as new products that you may recently have come into contact with.

Dr. Green utilizes T.R.U.E. Test (R) ready-to-use patch test for the diagnosis of the most common causes of allergic contact dermatitis. Common allergan that are tested in this manner include:

  • Nickel Sulfate
  • Wool Alchols
  • Neomycin Sulfate
  • Caine Mix
  • Fragrance Mix
  • Balsam of Peru
  • Colophony
  • Ethylenedidamine Dihydrochoride

How to prepare for your skin patch testing visit

Leading up to your visit, it is important to avoid sunlight, as ultraviolet rays can affect the immune system’s natural responses. In this same vein certain oral antihistamines, anti-depressants, heartburn medications, and oral steroids should be avoided in the few days leading up to the test, unless medically recommended. Additionally, your doctor may recommend that you abstain from taking certain prescribed immunosuppressant medications. Lastly, a patient should ideally be free of any active dermatitis symptoms on the back, which is the test site of the skin allergy patch testing.

On the day that the patches are applied, it is important that the skin is dry and free of any lotions, creams or oils. Once the patches are applied, exercise should be limited to avoid any sweat or twisting motions (which can lift up the skin patches).

An appointment is scheduled at the dermatology office after 48 hours to remove the allergen patches. Any initial reactions or contact dermatitis will be observed and the various patches will be marked. One further examination will take place, after an additional 48 hours, to observe the progression of any initial reactions or delayed reactions. Based on the degree of the reaction and the type of allergen, a proper diagnoses will be made and a list of allergens to avoid in the future will be reviewed.

Allergic contact dermatitis

Allergic contact dermatitis is defined as a skin irritation that is caused by direct contact with an allergen, whereas irritant contact dermatitis is caused by direct contact with a harsh substance. Unlike irritant contact dermatitis in which the rash typically stays where the irritant came into contact with the skin, allergic contact dermatitis leads to a more widespread rash, suggesting a stronger immune system response. Allergic contact dermatitis has several symptoms that are used to diagnose a positive patch test, including:

  • Red skin
  • Itchy skin
  • Swollen skin
  • Raised bumps or rough skin
  • Scaly, flaky, or cracking skin
  • Blisters, ulcers or lesions
  • Burning or pain

Though the effects of allergic contact dermatitis can be severe, patch testing itself is designed to apply a controlled amount of an allergen, reducing and limiting the amount of discomfort that can come from allergic contact dermatitis. If you think you may have allergic contact dermatitis, contact the office today to learn what your options are for diagnosis and treatment.

Skin allergies

Skin allergies are the standard cause of allergic contact dermatitis and can come from a variety of triggers. Common triggers include:

  • Pet Dander
  • Pollen
  • Poison Ivy
  • Irritating fibers or fabrics
  • Extreme temperatures (cold or hot)
  • Detergents and soaps
  • Sunscreens and bug sprays
  • Metals (found on jewelry or used as buttons)
  • Certain chemicals and foods

Skin allergies typically manifest as allergic contact dermatitis, but can also appear as hives or deep swelling in the dermis. If you think you may have a reaction due to a skin allergy, you can avoid items that likely caused the reaction, and contact the office for further guidance.

Understanding Skin Allergy Patch Testing

Skin allergy patch testing is used specifically for allergic contact dermatitis and symptoms directly affecting the skin. Unlike a skin prick test that uses needles to find a more immediate skin reaction, patch testing is used to find longer-term reactions and specifically aids in the diagnosis of skin conditions by determining if a skin rash is connected to a specific allergen or irritant. This can be important skin testing when it comes to skin conditions like atopic dermatitis (eczema) and psoriasis.

Patch testing is typically classified as a type IV sensitivity test, whereas a skin prick test is design to detect type I allergies. A skin prick test will help to diagnose conditions such as asthma, hay fever, food allergies, medication allergies, and any hives (contact urticaria) that might precede or indicate anaphylaxis (a near-immediate, life-threatening allergic reaction). If you feel you may have symptoms of type I (immediate reaction) allergies, it’s good to contact both your dermatologist and an allergist to learn what allergy testing will be best for you.

If you want a better approach to treatment for your skin rash or skin allergy, Dr. Michele Green can help you identify the cause of the problem and help create a solution for you. Contact us online today or call 212-535-3088 to find out how Skin Allergy Patch Testing can work for you.

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