Patient Instructions for Chemical Patch Testing

Bloomington-Normal Office 309-452-0995

Springfield Office 217-717-4404

Satellite Offices: Carlinville-Morton-Sherman-Jacksonville-Taylorville

Why is a Chemical Patch Test done?

The purpose of the patch test is to confirm allergens for common chemicals and metals that are suspected to

cause a contact reaction, also known as contact dermatitis, resulting in a rash after even brief exposure to the

skin. The rash that develops typically is delayed by 24 hours or more after contact to the skin is made. Due to

the delay, it can be difficult to correlate and identify the specific trigger of the rash with the timing of exposure.

The test is done to confirm what doctors call a “delayed-type” hypersensitivity, not an immediate Type 1

hypersensitivity (which is evaluated by Skin Allergy Prick Test). Up to 40% of patients with Atopic Dermatitis

(Allergic Eczema) also have Contact Dermatitis, which can make it difficult to control skin symptoms due to

unbeknownst continued exposure to allergens.

How is a Patch test done?

During the patch test, we will apply strips of chambers/wells filled with potential allergens to your back. The

allergens are a wide variety of chemicals that you may find in cosmetics, fragrances, rubbers, metals, etc. to

things that a person commonly touches. The chambers are attached to your skin by a weak adhesive tape. The

chambers must make constant contact with the skin for at least 48 hours. The chambers cannot get wet. After

at least 48 hours, the chambers are removed and the skin is evaluated for a reaction, which is usually a small

rash under the chamber where the chemical made contact with the skin. The rash may continue to erupt or

grow after the removal of the chambers, even as much as 7 days afterwards. It is important to continue

monitoring the skin areas where the tests are applied for any new rashes, for up to 1 week, and call our office

with any updates.

How will the Test make me feel and are there side effects?

The patches will usually be applied on the back and may occasionally feel uncomfortable, since you will be

wearing many “stickers” on your back for two or more days. You may develop itching under one or more of the

chambers. If itching and/or burning develop, try to avoid scratching----not only can it irritate the skin further, it

may also alter or invalidate test results. Severe allergic or irritant skin reactions may cause blistering in the area

under the patch chamber. Depending on your skin, a scar or pigmentation may develop after the severe rash or

blister heals. Due to the type of allergic reaction that is being testing, anaphylaxis does not occur during this

type of testing. If extreme itching, pain, or other problems occur, please contact our office immediately.

How do I prepare for the Patch test?

Shower and clean and skin before you come for your appointment. Wear loose clothing that is easy to remove

(including your bra), as we will need you to undress and may utilize your full back to apply the tests. Please do

not apply lotions to the back. You may treat other areas of rash. Antihistamines are OKAY to take. You must

not be taking any systemic corticosteroids (such as prednisone) for at least 14-21 days prior to the Patch test.

What do I do after the Test is applied?

Keep the area dry during the testing period. Showering or bathing is not allowed unless your doctor has used a

water-resistant covering. Avoid scrubbing, scratching, or rubbing the testing area. Avoid physical activities that

may cause excessive perspiration, or any activities requiring broad arm and should movement, as this could

cause detachment of the test unit. We also recommend that you wear loose clothing (such as a t-shirt) to bed,

Bloomington-Normal Office 309-452-0995

Springfield Office 217-717-4404

Satellite Offices: Carlinville-Morton-Sherman-Jacksonville-Taylorville

as this helps to prevent the test units from peeling or loosening. If you notices such loosening, have someone

apply pressure to the adhesive of the test unit to reapply it. If necessary, you can also apply additional paper

tape to the outside edges of the chamber units to keep them intact.

You will return to our office after 48 hours to have the chamber units removed by our staff. At this time, you

will have your first reading to determine if there are any positive results. A second reading for results is

conducted after 96 hours, which you will also return to our office for. Please remember to darken in any

marked areas for easier reading later. Do not cleans any marks or numbers that we have written with a marker

on your skin, as these markings are used to indicate which tests are applied at each location. Taking a photo of

your tests and skin each day is helpful to us to diagnose and keep track of your tests, especially in the follow-up

period after the tests are removed.

What results will I expect?

Positive reactions range from a small skin rash with a little swelling to red, blistered skin. Negative results are

also common. Patch testing helps to both determine and narrow the potential allergens that may be causing a

reaction. If you test negative on the initial testing, your doctor may have to test you again using another set of

allergens. This process of elimination will continue until the specific allergen is determined. Upon completion of

this procedure, you will be provided with the results and advised of any allergies you might have. The chemical

list that a person’s body is quite large. We cannot convey to you all the personal care products that you will

encounter in your daily life. As such, we will give you information on particular allergens, and what products

may contain these allergens. It is up to you to be in charge of your own health and to read labels and apprise

yourself of what chemicals you may be in contact with that causes a skin rash. The results of the allergy test will

serve as a guide to what products to avoid. Our allergy skin experts will also recommend bland products to help

assist you with finding alternatives personal care products to use, so that you can better eliminate allergy

triggers and start healing your skin.

Treatment Options

The only treatment for Allergic Contact Dermatitis (ACD) at this time is avoidance. The resources below will

assist you in education about ACD.

https://householdproducts.nlm.nih.gov/

https://www.contactdermatitisinstitute.com/database.php

https://medlineplus.gov/ency/article/000869.htm

https://www.contactderm.org/resources