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Allergic agony caused by caterpillars and moths

When I was very young, one of my friends faced a very irritating problem one evening while going home from school. We used to play under trees during the final two hours at school. During the walk back home too we had to pass beneath huge trees and walk beside bushes. Don't know how - a hairy, black caterpillar entered inside my friend's dress and started causing severe itching and rashes all over her body. She couldn't remove her clothes to check and throw away her tormentor in a public place even though she was very young then. Her shyness kept her going despite her pain. After reaching home, she developed more severe allergic reactions and had to visit a doctor. Since then we started avoiding trees and bushes that harbour these creatures during some seasons.

Why do we develop allergic reactions to caterpillars and moths?

The Lepidoptera is an order of insects that includes moths and butterflies. The larval stages of these insects are called commonly caterpillars and are completely different from their adult moth or butterfly forms, having a cylindrical body with a well-developed head, mandible mouth parts, three pairs of thoracic legs and from none up to five pairs of prolegs.

Most problems from caterpillar exposures are due to tiny hairs (setae) or actual spines on a caterpillar's body. Some cause allergic reactions. A few of these insects contain a toxin and can actually cause poisoning. For some caterpillars, their setae can blow on the breeze and land on skin, eyes, and clothing; this is common with gypsy moth caterpillars.

In order to defend themselves against predators, some caterpillars and moths have developed these hairs and/or sharp spines that may be directly irritating or capable of transmitting various toxins.

In most cases direct contact with the offending species is necessary to provoke a reaction. Some hairs get lodged in the skin of human beings. Occasionally the irritating hairs can be detached and dispersed by winds, causing large outbreaks of reactions in humans. These hairs may also surround cocoons, eggs (transferred from the abdomen of female moths), or other environmental objects. Hairs from some species, such as the oak processionary caterpillar, are stable in the environment for at least one year.

Studies have found that some larvae's hairs contain histamine, which can raise small red bumps and cause itching and even pain when it comes into contact with human skin. Pain, itching, and a rash are common. Blistering and swelling are possible. If setae blow into the eyes, eye irritation is expected.

Histamine is produced by the human body to dilate blood vessels. Slight skin swelling can result. Histamine is also the substance that causes redness and itching in allergies and bug bites.

Some individuals may develop allergic reactions to particular species of caterpillars and moths.

In very rare cases, spurs on the legs of large moths can penetrate human skin and cause stings, dermatitis or urticaria. Rare species of moths, from the genus Calyptra, are able to bite human skin in order to feed on blood. Reactions range from mildly itchy, papular urticaria (small red bumps and swelling) that resolves within an hour; to moderately itchy, urticarial, scaly, blistering, or widespread eczema-like reactions that can persist for weeks.

How can you reduce this agony? General first aid measures include:

Remove the caterpillar carefully with forceps or tweezers (bare hands should not be used to remove or squash the insect).
Sticky tape (especially duct tape) can be used to strip off any remaining hairs from the affected area. Then immediately wash the area with soap and water. Contaminated clothing should be removed and laundered thoroughly.

The rashes can be treated with lotions sold over the counter, such as calamine, but if the itching becomes more troublesome, or if more intense reactions occur, victims should seek medical attention.

'The art and science of survival' art work by Dr. Krishna Kuamri Challa

(from http://www.kkartfromscience.com )

If you have trouble with your skin - eczema, dry skin, itchiness, redness, rashes, etc - the cause could be dust mites. But it could also be moths - common clothes moths!
Moths are actually a significant cause of allergies, both indoors and outdoors. Exposure to the wing scales and other body parts of these flying insects can cause skin irritation and respiratory distress.

Moths may produce allergens other than their wing scales. If inhaled, the frass, or excrement, of a moth can elicit an allergic reaction. In addition, direct contact with many species of moths can cause skin irritation, due to the presence of urticating scales on the underside of the abdomen. These barbed scales can imbed into the skin, causing severe inflammation and itching. If inhaled, urticating scales can cause asthma and respiratory irritation.

A high frequency of sensitization to Bombyx mori was observed in a selected population of patients with respiratory allergic diseases (1). A study reported in Allergy found that almost 60% of people who react to dust mites are also sensitive to moths.

The adult clothes moth lays 50-150 eggs, usually in clothes, but sometimes in upholstered furniture, mattresses, bedding such as cotton sheets, or feather pillows.

Dislodged scales from adult moths can become a problem for some people who are exposed to these in large numbers, but it is the allergen produced by the clothes moth larvae, as they chomp their way through fabric, which is most likely to cause skin irritation.

To avoid this particular allergen, keep clean clothes wrapped in plastic coverings and don't leave soiled clothes lying around, especially not in dark corners - the favourite haunt of the clothes moth.

Maintenance of a good skin barrier is of paramount importance for anyone with a tendency to any skin problem. A good shielding lotion that bonds with the outer layer of the skin to form a protective barrier will help to keep out any allergen that might survive the moth control routine.

For those affected by moth allergies, the best course of action is to limit exposure to the insects. Many insect-rearing facilities have safety measures in place to limit workers' exposure to airborne allergens. Household moths can be controlled by storing clothes properly, or through the application of a pesticide. Serious moth infestations should be treated by a professional exterminator. Sensitive individuals should consult a physician to determine measures necessary to treat an allergic reaction to moths.

Tiger moths can cause lepidopterism, a severe and sometimes fatal allergic disease. Lepidopterism is often mistaken for dengue or chikungunya, because of similarities in symptoms.

Following scientific determination that Tiger moth, or Asota caricae, is responsible for unexplained fevers (2), researchers in Kerala state recently developed a kit capable of quickly diagnosing lepidopterism, a disease caused by moth allergen. Moth allergens are usually not taken into account in India, with patients getting erroneously treated for infectious fevers such as dengue and chikungunya. Delay in proper clinical treatment of lepidopterism often complicated related conditions like platelet drop, respiratory disorders, meconium aspiration syndrome and hepatic and renal failure. Without specific diagnosis, the actual, underlying disease can go undetected, often resulting in acute, and even fatal, respiratory problems. In India, these cases occur from June to August during monsoon season when moths flock to artificial lights.

The new ELISA-based test kit will address this problem when used for detection of Tiger moth disease in all Aster hospitals in India.

References:

1. http://www.sciencedirect.com/science/article/pii/S0021755713002301

2. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.01...

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