It's a clinical diagnosis
Atopic dermatitis is usually diagnosed clinically, and investigations are not required. The diagnosis rests on the pattern: what the skin looks like, where it is, how long it has behaved this way, how it itches, and what else runs in the family. That pattern is specific enough that a test would add little — which is why one isn't used, not because nobody got round to inventing one.
The distribution is doing a lot of work. Eczema tends to move with age — the face in infancy, the elbow and knee creases once a child is walking, the hands and neck in adults. It is usually roughly symmetrical, both sides at once. When someone glances at a rash and says "that's eczema" quickly, that is often what they read. See eczema in the creases.
When tests do have a role
- Patch testing should be considered particularly if the dermatitis becomes resistant to treatment — because a contact allergy sitting on top of eczema is a common reason for that. See patch testing.
- Swabs, if infection is suspected — see the signs of infection.
- Skin scrapings, if a fungal infection is in the picture — see when it's fungal, not eczema.
- A skin biopsy is occasionally used when the picture doesn't fit, or to separate eczema from psoriasis — see eczema or psoriasis?
What is not generally part of diagnosing eczema is broad food-allergy testing. That is a different question, answered for different reasons, and our guide on allergy testing for eczema explains why an "allergy panel" so often creates more confusion than it resolves.
What else it could be
The list of things that can look like atopic dermatitis is long. The ones that come up most: seborrhoeic dermatitis and psoriasis, contact dermatitis, and — in children — a set of rarer inherited conditions affecting the skin, immune system or metabolism. Fungal infection belongs on the list too.
Our guide on is it eczema — or something else? walks through the common impostors in more detail.
Severity gets assessed separately
Diagnosis answers "what is it". Severity answers "how bad", and it has its own instruments — EASI and SCORAD are the two developed to document how severe atopic eczema is. Those are two different conversations, and it's worth knowing which one you're in. See what the scores mean.
When to ask for another look
A clinical diagnosis is a judgement, and judgements can be revisited. Reasonable moments to ask:
- It isn't responding to treatment that should be working.
- It doesn't fit the usual distribution — one patch, one side, an odd border.
- It changed character, having been stable for years.
- It began in adulthood with no history behind it.
- It's severe enough to be shaping your life, and nobody has yet said the word "dermatologist".
"Could we revisit whether this is definitely eczema?" is a completely ordinary question, and a good clinician will not take it as a challenge. Our guide on talking to a doctor who feels rushed is there if asking feels hard.
Bring the pattern the diagnosis rests on
A clinical diagnosis is built from history — where, when, how long, what helped. Ollowen keeps that history as you live it, so the answer to “how has it actually been?” is a record instead of a reconstruction.
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Sources
- DermNet. Atopic dermatitis.
- American Academy of Dermatology. Could my child have eczema?
- National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIH). Atopic dermatitis.
- DermNet. Patch tests.
More Ollowen guides: see all →