Clive AndersonClive Anderson
PAPULAR URTICARIA is the term used to describe the numerous itchy bumps that appear on the skin as a result of insect bites. These bumps may be intensely itchy and persist for long periods, months and in some cases years.
Scratching leads to excoriations, which often become infected. When healed the lesions leave spots that may persist for long periods. The condition most often affects children, two to seven years, and is thought to be an allergic reaction to the insect bite. The location of the bumps is dependent on the insect involved, but commonly the arms and the legs are affected. Many different parasites, most commonly the cat or dog flea, the human flea, bedbugs, mosquitoes and some
biting flies can produce papular urticaria.
Mites are a common cause of insect bites. These insects cause injury to the skin while feeding and salivary proteins that are deposited during feeding cause the allergic reaction. Most mites feed and then fall off the skin. Dogs, cats and
rabbits frequently harbour mites. The pets may show no signs of the mite
infestation, however, the mites are highly contagious and handlers soon develop an itchy rash. Like most mites, they feed and fall off, returning to the animal host. The scabies mite is an exception as it burrows into the skin. This mite is transmitted by direct personal or sexual contact as the mite does not jump or fly.
TICKS
The average infected human has 1015 live adult female scabies mites on his or her body at a given time. After mating on the skin surface, the pregnant female burrows into the skin laying eggs at a rate of two to three per day. Scabies infestation is accompanied by severe itching especially at nights. Murine mites may affect persons working in areas infested by rats or mice.
Ticks are transferred to humans from domestic animals such as cats and dogs and cows. Often hungry ticks are to be found on tall grass or bushes waiting to attach themselves to passing persons. Ticks will spend up to 24 hours on the host's body searching for a good site to feed. The tick will feed on blood and when full, after up to seven days, falls off. Tick bites are not painful as an anaesthetic substance is injected into the skin. Most often the tick is seen or felt by the person while bathing. The bite is often red, and may become swollen and red. If the biting parts are left in the skin, when the tick is removed a deep swelling may develop. Sweat, warmth and white colours attract ticks.
Flies and mosquitoes cause wheals and bumps as a result of the irritating salivary secretions that are injected into the skin to prevent the blood clotting. Scents and bright colours attract mosquitoes.
WINGLESS INSECTS
The common bedbug is a nocturnal feeder coming out of hiding after persons have gone to bed. The insect does not fly but can run rapidly. When not feeding it lives in any dark place that it can find. Bedbugs are spread chiefly in clothing and baggage. The bites are painless and after feeding, the bedbug returns to its hiding place. Bites are usually multiple and may be arranged in a linear fashion. Bites that occur in threes are referred to as 'breakfast, lunch and dinner'. Some persons will develop an
allergic reaction to these bites with intense itching, wheals and papular urticaria.
Fleas are small wingless insects. They are capable of jumping to a height of seven inches. During feeding the flea uses a salivary secretion to slow coagulation of the blood. Flea saliva is very
irritating, producing an itchy rash. Fleas are one of the commonest causes of papular urticaria.
The best treatment for papular urticaria is to identify and remove the source of the insect bites. Disinfection of all pets along with fumigation of the home may be necessary. Topical steroids and antihistamines are used to control the itching. Topical or oral antibiotics may be necessary for infection. The use of topical insect repellants is useful.
Dr. Clive Anderson is a dermatologist and venereologist; email: yourhealth@gleanerjm.com.
