Exacerbating factor | Examples | Alternate explanations to consider |
Nonsteroidal antiinflammatory drugs (NSAIDs) | - Urticaria may worsen in patients within 24 hours after ingestion; some within 2 hours and others (particularly children) up to 4 to 24 hours later.
| - Consider alternate diagnosis of NSAID allergy or pseudoallergy if NSAIDs are the only or predominant trigger for hives or angioedema.
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Environmental conditions | | - Consider alternate diagnosis of cholinergic urticaria if hives are small (1 to 3 mm), surrounded by large areas of erythema, and predominantly triggered by changes in core body temperature (eg, exercise, hot showers, sweating, emotional factors).
- Consider exercise-induced anaphylaxis if hives only occur during exercise and not with passive changes in core body temperature.
- Consider cold urticaria or cold-associated inflammatory disorder if hives are exclusively triggered by exposure to cold.
- Consider solar urticaria if hives appear to be exclusively triggered by exposure to sunlight.
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Friction or pressure from clothing | - Hives may form under clothing straps, in areas where tight clothing compresses the skin, or in areas of natural friction (axillae, between thighs).
| - Consider diagnosis of delayed-pressure urticaria/angioedema if pressure on skin is followed in 4 to 24 hours by erythematous angioedema of affected area. Patients with delayed-pressure urticaria often have concomitant CSU.
- Consider vibratory urticaria if hives appear after exposure to vibration (eg, after clapping, mowing lawn, holding certain appliances).
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Alcohol | - Hives may be more numerous or severe after drinking alcoholic beverages.
| - If alcohol is the sole or predominant trigger, consider nonspecific reaction to histamine-releasing properties of some alcoholic beverage or, rarely, allergy to some component of the beverage.
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Opioid medications | - Hives may be more numerous or severe and pruritus more pronounced after taking opioids.
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Stress (emotional or physical) or sleep deprivation | - Hives can appear during stressful events, and/or control of chronic hives can be more difficult during stressful periods or periods of reduced sleep.
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Concomitant infections | - Hives can be more numerous or severe during viral illnesses (eg, common colds) or bacterial infections (eg, sinusitis).
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Menstruation or perimenstrual period | - Some females with CSU observe fluctuations with their menstrual cycle.
| - Consider alternate diagnoses of autoimmune progesterone dermatitis or other catamenial dermatoses if hives only occur in perimenstrual periods or lesions are not clearly urticarial.
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Irregular use of antihistamines | - Regular and consistent dosing of antihistamines is most effective in controlling CSU. Erratic or as-needed use may contribute to poor symptom control.
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