KUALA LUMPUR: It can happen in the middle of the night - an intensely itchy rash suddenly spreads across the body, disturbing sleep and leaving the person wondering what caused it. By the time they reach a clinic, however, the rash may have disappeared.
Dermatologist Dr Peter Ch’ng said this pattern is familiar to people living with chronic spontaneous urticaria (CSU). The condition causes recurring itchy, raised hives, sometimes with deeper swelling known as angioedema, for more than six weeks without an obvious external trigger.
“Normally, patients tell me, ‘Doctor, the rash disappeared while I was waiting to see you, but from experience, I’m certain it will come back again’,” he said.
For many patients, the problem extends beyond the skin. Repeated flare-ups and itching can affect sleep, concentration, work and emotional wellbeing, particularly because the next episode is often unpredictable.
Ch’ng said a typical urticaria rash has a smooth, swollen appearance, with individual hives usually disappearing within 24 hours. New ones may then emerge elsewhere, giving the impression that the rash is moving around the body.
Chronic urticaria affects around 1% of people worldwide, although estimates vary. A systematic review of Asian studies found a pooled prevalence of about 1.4%, though this included different forms of chronic urticaria rather than CSU alone.
Some patients mistake the rash for eczema, psoriasis or an allergic reaction. “Getting the diagnosis right matters because similar-looking conditions may require very different management,” Ch’ng said.
He added that haze has not been shown to directly trigger CSU, despite its known effects on conditions such as eczema, asthma and allergic rhinitis. Stress, however, may worsen urticaria in some people.
More than ‘just a rash’
A Malaysian study found that more than 80% of patients with CSU reported moderate-to-severe itching and hives, affecting work, social life and daily activities.
Ch’ng recalled treating a young patient whose symptoms were not adequately controlled by antihistamines, the usual first-line treatment. Frequent flare-ups affected his sleep and concentration, and he repeatedly missed classes.
Because hives can fade before a medical appointment, photographs can be particularly useful. Ch’ng advises patients to take clear pictures during a flare and note how the rash behaves.
Useful details include whether it is raised or flat, smooth or rough, whether each flare disappears within 24 hours and whether it leaves bruising or pigmentation behind.
Typical urticaria lesions are usually smooth and transient, disappearing within a day without leaving marks. Rashes that persist, scale, become painful or leave bruise-like changes may point to another condition and should be assessed.
Not every episode of hives is CSU, either. The six-week duration or recurrence threshold is one of the clues doctors use to distinguish chronic disease from a short-lived episode.
Some patients respond to new hives by repeatedly applying steroid cream wherever the rash appears. Ch’ng said this often makes little sense for a condition in which individual lesions vanish quickly and reappear elsewhere.
“Before the steroid cream is absorbed, the rash will likely have appeared on a different part of the body,” he said. “Chasing the rash with steroid cream is not the answer.”
He also cautions against repeated systemic steroid injections as a long-term solution, as they can carry significant health risks.
International guidelines recommend second-generation H1 antihistamines as first-line treatment, with treatment escalated under medical supervision if symptoms remain uncontrolled.
For Ch’ng, the goal is not merely partial improvement. "It is not enough to say the condition has improved by 50% when they still do not know when it will worsen. Clear, symptom-free skin is our target," he said.