A blister beetle encounter can result in a painful skin reaction due to a potent defensive chemical these insects produce. Blister beetles do not sting or bite; instead, they release a substance called cantharidin when they are crushed or disturbed. This colorless, odorless chemical causes blisters to form on the skin.
Identifying a Blister Beetle Bite
A reaction to a blister beetle, often called blister beetle dermatitis, typically manifests as a localized blister or welt on the skin. This reaction occurs because the cantharidin irritates the skin upon contact, not from an actual bite or sting. The affected area may appear as a raised, red patch with a fluid-filled blister.
Symptoms such as pain, burning, redness, and swelling often accompany these skin lesions. The reaction typically develops within 24 to 48 hours after contact, with some individuals noticing the blister upon waking. The blisters can contain yellowish fluid or even blood. Blister beetle dermatitis is usually temporary, with symptoms improving within about a week.
Treating the Bite and Managing the Blister
If a blister beetle lands on your skin, gently blow it off or carefully remove any clothing it has touched, rather than crushing it. After any skin contact with the beetle, thoroughly wash the affected area with soap and water as soon as possible to remove the cantharidin and prevent further irritation.
Once the area is clean, applying a cool compress can help to reduce swelling and provide some relief from pain and discomfort. It is important to avoid rubbing the affected skin, as this can spread the cantharidin to other areas of the body, including sensitive areas like the eyes, which can lead to more severe reactions.
It is generally advised not to pop or drain the blister, as opening it can increase the risk of infection. However, if a blister becomes very large and painful, some medical guidelines suggest carefully making a small hole with a sterile needle to drain the fluid, while leaving the skin intact to act as a natural bandage. After draining, gently press the blister with clean hands to remove the fluid. Regardless of whether the blister is drained, it should be protected with a loose, non-stick dressing to prevent further trauma and keep the area clean.
For symptom relief, over-the-counter pain relievers such as acetaminophen or ibuprofen can help manage pain. Topical corticosteroid creams, like hydrocortisone, can be applied to reduce itching and inflammation. Keep the blistered area clean and dry throughout the healing process. As the blister resolves, it will typically dry and crust over, eventually falling off within 5 to 10 days, leaving new skin underneath. While scarring is uncommon, some individuals may experience temporary discoloration of the skin.
When to Seek Professional Medical Care
While most blister beetle reactions can be managed at home, certain signs indicate the need for professional medical attention. If you observe signs of infection, such as increased redness, swelling that spreads, warmth around the blister, pus or fluid discharge, or persistent pain that worsens, a doctor should be consulted.
A fever or chills accompanying the skin reaction also warrant medical evaluation, as these can be signs of a systemic infection. Very large blisters, especially those that are particularly painful or involve a significant portion of the skin, may require medical assessment. Blisters located on sensitive areas like the eyes, mouth, nose, or genitals require immediate medical attention. If cantharidin gets into the eyes, it can cause pain, tearing, and decreased vision, requiring an eye doctor’s evaluation. Although rare, systemic reactions like nausea, vomiting, dizziness, rapid heart rate, or difficulty breathing, or signs of a severe allergic reaction (e.g., hives, facial swelling) require emergency medical care.
Preventing Future Encounters
Preventing future encounters with blister beetles involves being aware of their habitats and behaviors. Blister beetles are often found in gardens, fields, and areas with abundant flowers and crops. They are attracted to artificial lights at night, so keeping windows screened and outdoor lights off or using yellow/sodium vapor lights can help reduce their presence around your home.
When working outdoors in areas where blister beetles might be present, such as gardening or handling hay, wearing protective clothing, including long-sleeved shirts, long pants, and gloves, can minimize skin exposure. It is also advisable to shake out clothing, towels, and bedding that have been left outdoors before use. Inspect produce or firewood for beetles before bringing them inside can also prevent accidental contact. Managing weeds like pigweed, ironweed, and ragweed, which are attractive to blister beetles, can also help reduce their presence in your garden.