Some caterpillars, such as the gypsy moth, have hairs or fibers on their body which can break off, embed themselves in human skin, and irritate or transmit a toxin into the skin. Magnified, the barbed hairs resemble tiny versions of a porcupine’s quills, except that they contain a poison sac. Usually, it is necessary to touch the caterpillar to be stung, as the hairs are completely defensive and cannot be actively administered; but sometimes loose hairs can also cause irritation.
Most cases are caused by accidentally brushing against a caterpillar, although children may find these baroque caterpillars too fascinating to ignore. Sometimes loose hairs can be inhaled, causing breathing problems; or even injuring an eye. Touching some species of these caterpillars may cause only a mild tingling sensation, while touching other species may cause instant pain, followed by irritation for a period after and a raised, red weal or rash.
The severity of the injury depends partly on the sensitivity of the patient, the severity of the contact and the species of caterpillar. In most cases, symptoms are reddening and swelling of the skin and small bumps which are gone within the hour. More severe symptoms may include itchiness, blistering, or eczema-like symptoms which may last for weeks.
Antihistamine or hydro cortisol creams are usually effective. In their absence, an ice pack or a paste of baking soda will usually provide relief. Placing a piece of tape, preferably duct tape, on the affected skin and then pulling it off sharply is a good way of removing the hairs embedded in the skin. Wash the area well and wash all clothes thoroughly to remove any loose hairs which may remain.