The Diagnosis of Contact Dermatitis

To reach the diagnosis of contact dermatitis, it's essential to have the causative substance identified. We tell you more about it.
The Diagnosis of Contact Dermatitis

Last update: 16 December, 2022

Diagnosis of contact dermatitis can be straightforward in some cases. Especially if the trigger’s been identified (a poisonous plant, a cleaning product, or a dye, for example). However, in other cases, a more thorough examination may be necessary before confirming or ruling out the condition.

Contact dermatitis is a type of reaction that anyone can experience at some point in their life, regardless of gender, age, or lifestyle. Fortunately, most cases are mild and go away on their own in about 3 weeks.

But how do you know that it’s contact dermatitis and not another type of skin disorder? Let’s see the details below.


By paying attention to the causes, the location of the reaction, the symptoms, the duration, and evolution, many people can reach the diagnosis of contact dermatitis on their own. For example, if after wearing a piece of jewelry, you’ve experienced discomfort right in the area where the contact was direct (redness, itching, mild inflammation), you may have experienced a form of contact dermatitis.

Although jewelry (due to its nickel content) is a frequent trigger, some plants, cleaning products, hygiene products, and cosmetics are also triggers. Knowing about these triggers is helpful when doing a self-assessment at home.

At the same time, it’s good to consider if there’s a history of contact dermatitis or allergies in the family. This is because experts believe that those who have relatives with these types of problems are more likely to experience – at some point in their lives – some type of reaction.

Contact dermatitis on the skin.
It’s possible to self-diagnose contact dermatitis if the substance causing the reaction is known and there’s a direct history of encountering it.

If symptoms persist and worsen over time, seeing a doctor to receive the most appropriate treatment is essential.

Laboratory tests for the diagnosis of contact dermatitis

Although in many cases, contact dermatitis is a temporary problem that goes away on its own, in other cases, it may take longer. This raises questions about your diagnosis. So, depending on the severity of the symptoms, doctors may consider resorting to certain laboratory tests.

There’s no single test to diagnose irritant contact dermatitis. However, when allergic contact dermatitis is suspected, allergy skin tests, such as the patch test, can be used.

The True Test ® is a test approved by the US Food and Drug Administration (FDA). It’s used for the diagnosis of allergic contact dermatitis. Definitive diagnosis requires a positive test result, but not only that. There must be a history of dermatitis in the same area.

Differential diagnostics

There are many problems that cause rashes and reactions similar to contact dermatitis. Therefore, when there are doubts as to whether the reaction that the patient experiences may be contact dermatitis or another health problem, a differential diagnosis will be used.

The physician should consider whether the reaction is from an infection (systemic or skin), another form of dermatitis (seborrheic, atopic, dyshidrotic, herpetiform), psoriasis, or a mycosis fungoides. A skin biopsy or culture can be useful in this type of suspicion.

Both at the time of self-evaluation and in the medical consultation, it’s important to take into account that if other people living in the home experience the same reaction, then it’s not likely to be contact dermatitis. Contact dermatitis isn’t contagious.

Of course, if two or more people had contact with a poisonous plant (at work or on a walk outside) and both have the same reaction, it may be contact dermatitis. By asking the patient questions, the doctor will be able to obtain data that allow them to specify the diagnosis.

As indicated in a study entitled “The skin biopsy: fundamental bases. Part I” (“La biopsia cutánea: bases fundamentales. Parte I”):

“Biopsies occupy a central place in medical diagnosis, especially in dermatology, due to the easy access to the organ studied, and due to the valuable information obtained from histopathological examinations”.

The same source explains that biopsies are a useful procedure for specialists, as they allow them to support clinical suspicion and facilitate the correct diagnosis of contact dermatitis. They can also rule out dermatosis, vulgar psoriasis, pityriasis rubra pilaris, seborrheic dermatitis, atopic dermatitis, and mycosis fungoides.

Skin biopsy analyzed under a microscope.
Biopsies are very useful in dermatology. When in doubt, they allow doctors to clarify a diagnosis.

Diagnosing Atopic Dermatitis Helps Us Take Action

Even when it’s possible to reach the diagnosis of contact dermatitis on your own and it goes away in a short period of time, it’s important to be cautious and observe the evolution of the reaction. Having precision about the condition will allow you to eliminate the agents associated with the disorder.

Reducing exposure to allergens is a viable solution in most cases. When the contact can’t be removed for work reasons, then other measures are applied. Either way, this step is only possible with a proper diagnosis.

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