Second Location: Beginning in August 2026, we will see patients on Tuesdays at our new location: 8888 Ladue Road, Suite 105, St. Louis. Our primary location at 4800 Mexico Rd in St. Peters will be closed on Tuesdays. We look forward to welcoming you to our new space!

Find the cause of your skin reactions.

Patch Testing in St. Louis, Missouri

If you have a rash that keeps coming back, patch testing may help identify the cause. Dr. Sonia Cajigal is a board-certified allergist in St. Louis, Missouri who helps adults and children evaluate allergic contact dermatitis and other delayed skin reactions. Learn what patch testing is, what it can diagnose, and what to expect during the process. Schedule your visit today!

“Had my first appointment with Dr. Cajigal. She’s wonderful. A different doctor had said there wasn’t much I could do for my allergies, except maybe move out of state. I was desperate and came to the doctor for help. She listened and was very thorough in her diagnosing my problems. I’m not better yet but I’m very pleased with how this appointment went and I’m optimistic about my health!”

– Rosana B, November 2021

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Patch Testing Doctor Sonia Cajigal of St. Louis Family Allergy in St. Louis, Missouri
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About Patch Testing

Overview

When to Patch Test?

What Can it Diagnose?

What to Expect

Understanding Results

Patch testing is used to find out whether your skin is reacting to something it touches. This type of testing is most often used when allergic contact dermatitis is suspected. Unlike skin prick testing, which looks for immediate allergy symptoms, patch testing is designed to identify delayed skin reactions that can show up over several days.

Common triggers include metals, fragrances, preservatives, rubbers, adhesives, and certain medications.

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in St. Louis, Missouri

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Skin patch testing for allergic contact dermatitis

When Patch Testing Is Recommended

Patch testing may be recommended if you have:

  • a rash that keeps returning
  • eczema that does not fully improve
  • a reaction linked to cosmetics, lotions, soaps, or topical products
  • irritation from jewelry, adhesives, gloves, or workplace materials
  • chronic hand dermatitis
  • eyelid, facial, neck, or underarm dermatitis
  • a rash that seems worse after contact with specific products

What Is Patch Testing?

During patch testing, very small chambers containing different potential allergens are placed on your back with tape. These chambers stay in place for several days so the skin can be observed for a delayed reaction.

Patch testing does not look for food allergy or immediate allergic reactions. Its purpose is to help determine whether a delayed skin allergy is contributing to your rash.

What Can Patch Testing Diagnose?

Patch testing is most commonly used to evaluate allergic contact dermatitis. This is a type of skin allergy that happens when your immune system reacts to a substance after it touches your skin.

Reactions may develop from:

  • fragrance ingredients
  • preservatives in skin care products
  • metals such as nickel
  • rubber chemicals
  • adhesives
  • topical antibiotics
  • hair dye ingredients
  • nail product chemicals
  • workplace exposures
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in St. Louis, Missouri

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Girl in need of patch testing with allergic contact dermatitis rash near neck

What to Expect During Patch Testing

Patch testing is usually completed over multiple visits. At the first visit, the allergen panels are placed on your back. You will then return so the patches can be removed and your skin examined. Because delayed reactions may take time to appear, the skin is often checked again after additional time has passed.

While the patches are in place, you may be asked to avoid getting your back wet or doing activities that cause excessive sweating so the test remains readable. The exact instructions can vary depending on the testing plan and your skin condition.

Understanding Patch Testing Results

A positive patch test means your skin reacted to a specific substance. The next step is figuring out whether that allergen is actually relevant to your rash. In many cases, the most important part of patch testing is not just identifying the allergen, but learning where it is found and how to avoid it in your daily life.

That can be especially helpful for patients who have tried switching products on their own without success. In some cases, the problem is not the product category itself, but a specific ingredient that appears in multiple products.

Patch Testing vs. Other Allergy Tests

At St. Louis Family Allergy, testing is tailored to the type of reaction you may be having. Patch testing is used when delayed skin reactions or allergic contact dermatitis are suspected.

Other types of allergy testing may be used for immediate allergic reactions, environmental allergies, food allergies, or medication allergies. Your evaluation will help determine which type of testing is most appropriate.

Schedule Patch Testing in St. Louis

If you have a rash that keeps returning or you suspect your skin is reacting to something you use every day, patch testing may help identify the cause. Dr. Sonia Cajigal provides personalized allergy evaluation for adults and children in St. Louis, St. Peters, and surrounding Missouri communities.

References

[1] American College of Allergy, Asthma & Immunology: https://acaai.org/
[2] Asthma and Allergy Foundation of America: https://www.aafa.org/
More Specialties

Asthma

Drug Allergies

Eye Allergies

Food Allergies

Nasal Allergies

Skin Allergies

Allergy Shots

Allergy Testing

Biologic Therapy

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Visit Allergist Dr. Sonia Cajigal of St. Louis Family Allergy in St. Louis, Missouri

Skin Allergy Doctor
Dr. Sonia Cajigal

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St. Louis Family Allergy Google review score badge
"Dr. Cajigal was friendly, professional, and informative. She took the time to explain the tests and what was going on with my allergies. She is so knowledgeable and really cared about how I was feeling. I would highly recommend this practice if you suffer from allergies and asthma."

- Sue D, July 2020

“Dr Cajigal is a great listener. She trusts her patients instead of treating them as if they are not the experts of their own bodies. I really appreciate that (many doctors do not have that quality). She also immediately treats the symptoms instead of waiting to see if things clear. I use her for my children and myself. We have never left her office feeling as if it was a waste of time.”

– Stephanie, August 2020

"Great Allergist!"

- Ann H, December 2018

"She is the best."

- Stephen W, June 2020

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We are currently accepting new adult and pediatric patients at St. Louis Family Allergy!

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