Caterpillar Dermatitis – Causes, Symptoms & Treatment


Caterpillar dermatitis is a skin condition caused by the caterpillars of the processionary moth . Contact with the nettle hairs of these caterpillars triggers an allergic reaction that leads to a typical complexion. At the same time, respiratory problems and conjunctivitis can also occur. Caterpillar dermatitis occurs almost exclusively in the summer months.

What is caterpillar dermatitis?

Caterpillar dermatitis is a contact allergy . If the skin comes into contact with the hair of the caterpillars, especially the oak processionary moth, an allergic reaction is triggered by the venom they contain.

The resulting dermatosis is characterized by sharply defined redness and severely itchy nodules or papules. In some cases, other allergic reactions occur in addition to the typical skin changes.

In addition to conjunctivitis, these include diseases of the respiratory tract. Caterpillar dermatitis can also lead to sore throats, bronchitis and asthmatic symptoms. In very severe cases, anaphylactic shock is possible.


The caterpillar dermatitis occurs mainly in the period from April to September, when the caterpillars of the processionary moth are on the move and can occur locally in very large numbers.

You don’t have to have direct physical contact with the caterpillars themselves to get sick. It is enough to come into contact with the caterpillars’ hairs, which they lose in large quantities during their migration through forested areas and which can remain suspended in the air or on the ground or in the undergrowth for longer periods of time.

The hairs of the processionary caterpillars are two to three millimeters long nettle hairs that adhere firmly to the skin with barbs. These contain the nettle toxin thaumetopoein, a protein released when hair breaks off.

The body reacts to this by releasing histamine , which manifests itself with redness, itching and other allergic reactions that result in the typical clinical picture of caterpillar dermatitis.

Symptoms, Ailments & Signs

The first symptoms of caterpillar dermatitis appear shortly after the skin has come into contact with the fine and toxic stinging hairs. Itching , skin irritation and rashes are the most common . Typically, this results in the formation of itchy bumps that can resemble those of insect bites.

After some time, it causes severe burning wheals or papules . The affected skin areas are severely irritated and reddened. As a rule, uncovered areas such as the face, neck or arms are particularly affected. Sometimes the itchy rash can also appear on the neck, legs, or back.

After some time, a general malaise appears. In many cases, fever and chills occur. The penetration of the nettle poison causes the body to release histamine. This can lead to pseudoallergic reactions such as shortness of breath . Allergy sufferers are particularly affected.

If the nettle hairs come into contact with the eyes, irritation of the mucous membrane of the eyes occurs, which can develop into conjunctivitis. The eyelids can swell severely. If the nettle hairs are inhaled, the mucous membranes in the throat and neck area are also irritated. This can lead to coughing , shortness of breath, swelling and asthma attacks . The symptoms can sometimes last for up to several months.

Diagnosis & History

Caterpillar dermatitis becomes noticeable shortly after contact with the nettle hairs of the caterpillars of the processionary moth. Clearly demarcated redness and severely itchy nodules, papules or wheals appear on the skin regions not covered by clothing.

The affected areas may swell slightly and feel warm. Scratching can also inflame the skin. Caterpillar dermatitis is often accompanied by an increased body temperature, dizzy spells and a general feeling of being unwell.

Conjunctivitis can also occur if caterpillar hairs get into the eyes as well. Other common accompanying symptoms of caterpillar dermatitis are inflammation in the throat area and coughing, since the hair can also be inhaled.


Various complications can occur as a result of caterpillar dermatitis. If the disease is not treated promptly, severe fever and chills often occur. In rare cases, these symptoms can lead to circulatory collapse. If the fine hairs get into the eyes, it can cause conjunctivitis.

If they get into the airways, this leads to shortness of breath and, in rare cases, to asthmatic attacks. Anaphylactic shock can also occur due to a strong immune reaction of the body. In general, caterpillar dermatitis is associated with severe discomfort. The quality of life of those affected is reduced accordingly and mental suffering can sometimes also occur.

Even with the treatment, complications cannot be ruled out. Prescribed medications such as antihistamines and corticosteroids can cause symptoms. Gastrointestinal problems, headaches, muscle and body aches and other side effects are typical. In isolated cases, circulatory collapse occurs in children, the elderly and the sick.

If other medications are taken at the same time, interactions cannot be ruled out. Allergic reactions can exacerbate the original symptoms and represent one of the most serious complications in the treatment of caterpillar dermatitis.

When should you go to the doctor?

In the case of caterpillar dermatitis, it is not absolutely necessary to see a doctor. The disease usually heals on its own. If the symptoms last longer than three weeks or get worse, the family doctor should be the right person to talk to.

Even if the symptoms are disproportionately strong, a doctor should be consulted. In some cases, those affected also suffer from fever, swelling or even difficulty breathing. In acute emergencies, the hospital can also be visited directly or the emergency doctor can be called.

Treatment & Therapy

Caterpillar dermatitis is usually completely harmless and, if left untreated, heals within two to three weeks. To relieve the itching, the affected skin areas can be mechanically cooled or cortisone-containing ointments applied.

The administration of antihistamines can also be useful. Scratching should be avoided at all costs, as this not only spreads the hair of the caterpillars, but can also inflame the skin. In the event of severe symptoms, it is always advisable to consult a doctor.


To prevent caterpillar dermatitis , it is best to avoid areas known to be infested with processionary moth caterpillars during the period from April to September.

If this is not possible, clothing should be used to cover as large an area of ​​the skin as possible. This clothing should be removed as soon as you return and washed at at least 60°C to remove the caterpillar hairs that are stuck to it. Visible nettle hairs must be removed from the skin immediately. After that, the entire body should be washed thoroughly in the shower.

If possible, any objects carried should also be cleaned with water, if possible. If an infestation with oak processionary moths is found in a previously caterpillar-free area, this should be reported immediately to the responsible authorities so that professional elimination can take place.


In most cases, those affected with caterpillar dermatitis have only very few and only very limited measures or options for direct aftercare. This should therefore contact a doctor as soon as the first symptoms or signs of the disease appear, so that there are no further complications or complaints. Caterpillar dermatitis cannot heal itself.

Affected people are often dependent on a surgical procedure, which usually also requires radiation therapy or chemotherapy. Regular check-ups by a doctor are also very important after the removal in order to identify and treat further tumors at an early stage. Further aftercare measures are not available to those affected with caterpillar dermatitis.

In many cases, caterpillar dermatitis limits the life expectancy of those affected, although a general course cannot be predicted. The focus is therefore first and foremost on early detection and diagnosis of the disease. In some cases, contact with other people affected by the disease can also be very useful, as this can lead to an exchange of information, which makes everyday life easier for the person affected.

You can do that yourself

In caterpillar dermatitis, the hairs of the oak processionary moth have lodged in the patient’s skin. The more toxic nettle hairs that are able to settle in the patient’s tissue, the more severe the symptoms are. They range from a skin rash to a severe allergic reaction with fever, chills and/or shortness of breath. Anaphylactic shocks are also possible. Therefore, those affected should immediately consult a doctor or call an ambulance in the event of severe symptoms.

However, if the contaminated areas on the body are limited, the disease can heal without medical help. Freely available cortisone ointments and cooling compresses help against the swelling and itching of the rash. Scratching would aggravate the symptoms because it spreads the nettle hairs further or drives them deeper into the tissue. Scratching could also inflame your skin.

The patient should allow himself and his body to rest during this time. So that the symptoms do not unnecessarily worsen, allergy sufferers can take their medication (usually antihistamines ) as a precaution, since the body releases histamine due to the nettle toxin and thus aggravates existing allergies. If there is a risk that nettle hairs have gotten into your eyes, it is advisable to consult an ophthalmologist . In an acute case, it helps to wash out the eyes with clear water, but not to rub them.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.