SINGAPORE: The Chinese New Year (CNY) period can be a time when some individuals develop new or worsening itchy, red swellings on their skin.
They may attribute the itch to eating seasonal festive food that they do not usually eat, or taking medicine such as painkillers to quell a late-night, post-mahjong headache.
Some people may find dressing up in new but body-hugging clothes for CNY visiting a factor. For others, even the strap of a handbag loaded with mandarin oranges can cause an irksome itch on the shoulder.
These raised wheals that dermatologists and general practitioners see in the clinics are likely to be caused by urticaria, also known as hives. They can occur suddenly, only to subside hours later without a trace. But what can make urticaria appear persistent is that when some wheals subside, new ones may appear elsewhere.
Any part of the body can be affected. When the eyelids or lips are involved, the resulting puffiness is known as angioedema.
Urticaria can occur at any age, and in any gender or ethnicity. Globally, it affects about one per cent of the population.
Urticaria is caused by the release of histamines by mast cells, a type of white blood cell, in the skin. Histamines are chemicals that contribute to the very symptoms of urticaria: Increased blood flow, sensitised nerve endings, and inflammation. Histamines are rapidly broken down by the body, which explains the short duration of the wheals.
INFECTIONS AND MEDICATIONS
The common triggers of urticaria are infections and medicines such as painkillers and antibiotics, which explain why people develop urticaria when they fall sick.
Potential triggers are identified from the patient’s history. If an infection or medicine is the cause, the wheals should subside once the infection or medication use ceases.
EXTERNAL AND INTERNAL FACTORS
Urticaria that persists for more than six weeks is known as chronic urticaria. It is immensely frustrating for the sufferer as the symptoms can appear without provocation, and may worsen with emotional stress or exercise.
Unlike acute urticaria, chronic urticaria is seldom attributed to an allergic cause. However, physical factors such as direct pressure on the skin, and changes in environmental temperature can induce the wheals.
Some research points to the production of antibodies by the body’s immune system that trigger the mast cells to release histamines. Abnormalities in blood coagulation may also play a role.
Urticaria associated with food tends to begin in childhood. The symptoms typically appear soon after eating specific foods.
Although often suspected by patients, studies have not found food allergies to be a significant factor in chronic urticaria. Instead, some theories suggest that it is the preservatives and colouring agents in some foods that may contain histamines or histamine-releasing chemicals.
Doctors first determine the likelihood of a suspected food allergy from the patient’s history. Provocation tests are only offered if the patient's history is corroborative as the tests are not without risks. This involves exposing the patient to the suspected trigger food and looking for any reaction.
Certain rare diseases do count chronic urticaria as a symptom and laboratory tests may be performed to diagnose them. Tests may also pick up other autoimmune diseases, especially those concerning the thyroid gland.
Most cases of urticaria are effectively controlled with antihistamines. These should be taken long-term in patients with chronic urticaria. Drugs that suppress the immune system or block offending antibodies, are used in patients who do not respond to antihistamines.
KEEPING URTICARIA AT BAY
With many CNY activities that can potentially trigger urticaria, should you be worried? Probably not, especially if you do not have urticaria.
If you are a patient, take your antihistamines regularly to mitigate flare-ups. Your doctor or pharmacist can help you select a non-sedating, long-acting antihistamine.
Try to keep cool and wear loose clothing before you head outside. If you are concerned about the banquet food or alcohol, consume them in moderation and limit them to only what you have eaten without incident.
Dr Tee Shang-Ian is a consultant at the National Skin Centre, which is part of the National Healthcare Group.