Dermatology 101: diagnosing a transient rash as urticaria

In this video, you'll learn strategies to recognize and treat this condition and how to make sure you don't confuse it with more serious conditions.

Paul Scheidegger, MD
Paul Scheidegger, MD
1st Jul 2021 • 2m read

The most likely cause of a transient rash is urticaria–but that's not always the case. In this video, you'll learn strategies to recognize and treat this condition in patients with varying complexions and how to make sure you don't confuse it with more serious conditions.

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Video transcript

The most likely cause of transient rash is urticaria. In this Medmastery lesson you will learn strategies to recognize and treat this condition. Patients with urticaria present with wheals or hives, angioedema known as swellings, or both. Urticaria can affect any side of the body and tends to be widely distributed. Urticarial hives can be colored white, or red, and may be surrounded by a red flare.

These can be round or form giant patches. They are typically very itchy and move around within six to 12 hours. It is important to know that the redness surrounding hives in urticaria patients with darker skin may be more subtle. In these patients hives will appear as swollen or raised bumps and will typically spread over a larger area of skin compared with what is observed on patients with light skin.

Angioedema is a swelling of the skin or mucous membrane. The presence of angioedema in the mouth indicates a more urgent dermatological condition because the swelling may be obstructing the upper airway. And if a patient presents with angioedema in the mouth in the absence of hives, this may indicate life threatening conditions, such as hereditary or acquired angioedema.

So they should immediately be given a systemic steroid, antihistamine and sometimes even adrenalin. Urticaria can either be acute or chronic in patients with acute urticaria. The hives are present for less than six weeks and typically resolve on their own. In those with the chronic form hives are present for longer than six weeks.

Chronic urticaria is often referred to as idiopathic, meaning the exact cause is unknown, but it is likely caused by an autoimmune mechanism. The most common form of chronic urticaria is urticaria factitia, which is characterized by redness and swelling following a minor stroke, rub or scratch of the skin.

The main treatment of all forms of urticaria in adults and children is an oral second generation antihistamine. If the standard dose, for example 10 milligrams of loratadine, is not effective, the dose can be increased up to fourfold so 240 milligrams of loratidine daily. Once the urticaria has settled down, the treatment should be stopped. So remember, any widespread itchy rash that is transient or moves around within six to 12 hours should be considered urticaria until proven otherwise.

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