Cholinergic Urticaria Workup

Updated: Mar 06, 2018
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
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Workup

Approach Considerations

Traditionally, an intradermal injection of either 0.05 mL of 0.002% carbamylcholine chloride (carbachol) or 0.05 mL of 0.02% (0.01 mg) methacholine has been used to produce a flare-up of cholinergic urticaria containing characteristic wheals, often with satellites. This outcome occurs in about 51% of patients. The same flare-up may occur in persons without this condition, but it is usually smaller and without whealing.

Nicotinic acid has also been used at a dilution of 1:500,000 or 1:100,000. Lesions of cholinergic urticaria have even been reproduced by curare derivatives such as D-tubocurarine.

Cholinergic dermographism can be reproduced by stroking the skin, by using methyl acetylcholine, or by using other stimuli that cause sweating.

The demonstration of sweat-specific immunoglobulin E in cholinergic urticaria patients who are unable to provide sufficient sweat may be facilitated by use of iontophoresis with pilocarpine nitrate. [24]