This morning, a 40-year-old woman called a question into my radio talk show complaining of a bunch of tight blisters under her right shoulder blade. She said, “The skin is red underneath and the whole area is quite painful.” Her question was, “What kind of bug bites could have done this, and what should I do?”

In reality, these were likely not bug bites, but rather the manifestations of the alphaherpesvirus varicella-zoster virus (VZV).

This virus is more commonly referred to as “chickenpox” early in life and “shingles” when it reemerges in older individuals. Though we typically acquire chickenpox at a young age, the virus sets up shop in peripheral nerves for the lifespan of the host and can raise its ugly head many years later, resulting in shingles.

It is fortunate that vaccination of the young, or those over 60 years, can help prevent chicken pox and reduce the severity of shingles if the virus ever reactivates.

A similar type of skin infection can be caused by herpes simplex virus (HSV). Infection with HSV commonly results in fever blisters, also known as “cold sores.”

These are larger, painful, blisters which cluster around the infected area, typically the mouth or the genitals (depending on where the virus was initially acquired) that can reemerge when the immune system is weakened by illness or stress.

There are two types of HSV, I and II, that can be both directly and sexually transmitted. Like VZV, HSV type I and II are alphaherpesviruses, meaning they also exist for the lifespan of the host. Antiviral medications like Acyclovir can help abate symptoms and prevent reactivation, but there are currently no vaccines or cures available for HSV.

Blisters can also result from contact dermatitis, a condition in which the body reacts negatively to an irritant or allergen, resulting in a skin rash.

These irritants or allergens can be anything, like poison ivy, antibiotic ointment, or even fabric softener.

We also see blisters pop-up when unprotected hands are traumatized by raking the yard, burned by grabbing a hot pot handle, or frost-bitten on an ice-fishing expedition.

A life-threatening blister condition can also occur when a person has an allergic reaction to some pill or intravenous medicine and blisters start spreading over extensive amounts of skin and into mucous membranes. When this occurs, stopping the culprit medicine and providing emergency medical measures can save the patient’s life.

A few years ago, a 99-year-old patient started suffering from blisters over her lower legs. I first tried stopping every unnecessary medication, then a topical treatment, but to no avail. I reviewed causes for blisters and once again realized how many different reasons there could be for blisters on the skin.

After biopsy, her diagnosis came back as a mysterious autoimmune disorder called pemphigoid. The dermatologist treated and cleared the blisters with just the right medicine, and my patient had relief.

The more I learn, the more I am humbled.