Updated: Aug 3
Nature's toxic defenders, the Blister Beetles, hold many secrets worth discovering. These ubiquitous nuisances are commonly found in fields, gardens, and even around outdoor lights during the evenings. What sets them apart from other insects is their ability to produce a chemical that induces blister formation on human skin.
They have aptly earned the name "blister beetles." So far in my career as a dermatologist, I have seen and treated innumerable cases. Drawing on my experience, this article will delve into the world of blister beetle bites, explore their habitat, understand the blister-causing process, and learn effective treatment methods.
Table of Contents
Where are Blister Beetles Found?
Blister beetles are a prevalent nuisance in fields and gardens. Blister beetles commonly reside in flower beds, grassy areas, and around outdoor lights during the evenings. Light, especially ultraviolet light, attracts blister beetles.
They are commonly found in tropical regions of the world, including Central and South America, Western Europe, Sudan, Senegal, India, and Nigeria.
What are Blister Beetles?
They belong to three biological families, namely Meloidae, Staphylinidae, and Oedemeridae. There are over 2,500 species of blister beetles distributed among at least 120 genera. These beetles can be yellow, grey, brown, or black.
While they share similar body types and behaviors, they commonly affect human health by producing a chemical that induces blister formation on and beneath the skin. In the past, certain species of blister beetles were consumed as aphrodisiacs, but this practice is hazardous and should be avoided at all costs.
What causes Blister Beetle Blisters?
Blister beetles are most renowned for their ability to secrete substances that cause skin welts when injured or crushed. They secrete toxins like cantharidin (found in families Meloidae and Oedemeridae) or pederin (present in the genus Paederus). Cantharidin is also used in treating pox virus lesions.
Cantharidin and Pedrin are odorless and colorless substances. Cantharidin is a potent tissue-destroying agent utilized in products designed for wart removal. Although the toxin is highly lethal to the beetle's enemies, it is not harmful to human skin. However, contact with Cantharidin or Pedrin can lead to a localized reaction.
What Does a Blister Beetle Bite Look Like?
Contrary to popular belief, blister beetle does not cause an insect bite or sting. Blister beetles do not possess stingers, and their jaws are not strong enough to break human skin. Instead, the welts or blisters on the skin result from contact with the beetle's chemical defense mechanism.
When people accidentally rub the insect against the skin's surface, it causes blister beetle dermatitis. The crushed beetle then secretes toxins that induce irritant reactions on the skin, forming blisters.
What are Blister Beetle Bite Symptoms?
Blister beetle dermatitis causes localized vesicles, blisters, or welts that may be red and raised. The affected area might experience pain, burning, redness, and swelling. Symptoms usually appear within 24 to 48 hours after contact with a blister beetle, sometimes being noticed after waking up in the morning.
There might be the formation of sacks of yellowish fluid, hemorrhagic fluid, and pus in the blisters. However, these blisters are temporary and tend to improve within a week, turning into crusts. Though there is a low risk of scarring, some individuals might experience post-inflammatory hyperpigmentation.
There is also a risk of secondary infection. When exposed on the knees, elbows, or similar skin folds, the resulting lesions can occur on opposing surfaces that come into contact, referred to as "kissing lesions."
Rove Beetle Bite Symptoms
Rove beetles are also a type of blister beetle belonging to the family Staphylinidae. They cause Paederus Dermatitis, an irritant skin condition caused by contact with pederin present in the rove beetle species, including the Nairobi fly. They also produce localized redness, swelling and blistering unrelated to the blister beetles' cantharidin reaction.
Other names of rove beetle rash are night burn, spider lick, or Nairobi fly rash.
The skin develops a blistering rash within 24 to 48 hours after coming into contact with or crushing the beetle on the skin. Its treatment is similar to other forms of blister beetle dermatitis.
How to Treat a Blister Beetle Bite?
Wash the affected area daily with warm, soapy water to treat a blister beetle bite. A cold compress can also help alleviate swelling and pain several times daily.
According to a BMJ Study, the most effective dressing combinations for blister beetle dermatitis is the initial use of povidone-iodine (Check out betadine) and hydrocolloid gel (You can also try out hydrocolloid bandages).
Your dermatologist might also recommend the application of a topical steroid, silver sulfadiazine dressings for ten days, or an antibiotic to prevent secondary infection. In severe situations, it might be necessary to seek medical attention, particularly if cantharidin gets in your eyes or if you accidentally swallow blister beetles or products containing them.
Do Blister Beetle Bites Itch?
Yes, blister beetle dermatitis can cause itching in the affected area due to the skin's inflammatory response to cantharidin. You might also experience localized burning, pain, stinging sensation, and itching.
What Happens if a Blister Beetle Bites you?
Blister beetle dermatitis occurs when a blister beetle comes into contact with the skin, releasing cantharidin, which causes blisters and welts on the affected area.
What are the Signs of Blister Beetle Poisoning?
Blister beetle poisoning is not a concern for humans regarding blister beetle dermatitis. However, ingesting large amounts of cantharidin, which is present in blister beetles, can be poisonous and cause severe symptoms like mouth burning, nausea, and gastrointestinal hemorrhaging.
Do Blister Beetles Bite or Sting People?
Blister beetles do not bite or sting people. The welts and blisters on the skin result from contact with the beetle's chemical defense mechanism, cantharidin, released to protect the insect from enemies.
How Can I Get Rid of Blister Beetles in My Garden?
For local infestations, the most practical approach is handpicking the beetles. Wearing gardening gloves can protect your hands from potential blisters. On commercial farms facing blister beetle infestations, pesticide application may be necessary.
If you are concerned about dark spots occurring after a mosquito bite, you can read my article on How to Remove Dark Spots Caused by Insect Bites or Mosquito Bites?