An Unusual Itch

This week’s reflection is about a patient who had no visible rash at all — yet came to see me with intense itching.

These are the consultations where the history matters most. With further probing, a clear pattern emerged: the itch was triggered by anything that induced sweating. Exercise, entering a hot room, even emotional arousal — all would provoke the same sensation. He described it vividly: “It feels like I’m about to sweat, but instead I just itch.”

Most Dermatologists are familiar with cholinergic urticaria, where heat or exertion leads to urticarial wheals. What was different here was the absence of any visible skin change — just pruritus.

When a Doctor doesn’t know…

This was the sort of consultation where I knew enough to document the symptoms and loosely label the condition, but not enough to establish a firm diagnosis. In Dermatology this happens - as there are over 3000 skin conditions and there are some we won’t have encountered or even read about. My role in this case is to know how to describe the symptoms and know where to look in the literature.

Does cholinergic pruritus exist?

Cholinergic pruritus does exist in the literature, though it’s far less well described than cholinergic urticaria. Some authors view it as part of a spectrum — perhaps even a precursor to cholinergic urticaria in certain patients.

There isn’t a robust evidence base for treatment, but the suggested approach broadly mirrors that used for cholinergic urticaria:

• High-dose antihistamines (up to four times daily)

• Consideration of second-line agents such as danazol

• One report of omalizumab being effective

My initial approach

I decided to treat this primarily as a pruritus presentation while also keeping an open mind about systemic drivers.

Management included:

• High-dose antihistamines

• 2% menthol cream for symptomatic relief

• An itch blood screen to exclude systemic causes — particularly a paraprotein or other metabolic contributors

I also wondered whether antimuscarinic agents used for hyperhidrosis might help, given the sweat-related trigger. However, the literature doesn’t really support this, so for now I’ve kept it as a theoretical rather than practical option.

Take-home

Not all cholinergic symptoms produce a rash. When patients describe exertion- or heat-induced itch without visible change, cholinergic pruritus is worth considering — and management may need to follow the urticaria pathway even in the absence of wheals.

I’ll be interested to see how he responds and will update in due course.

First published at: https://open.substack.com/pub/draaronhughes/p/an-unusual-itch-75f?r=7c1gox&utm_campaign=post&utm_medium=web&showWelcomeOnShare=true