Final answer:
Blister formation on non-blistered skin due to lateral pressure or rubbing is a protective response to skin trauma. Friction, burns, infections, and allergic reactions are common causes. The epidermis and sometimes the upper dermis are the affected layers of the skin.
Step-by-step explanation:
Lateral pressure or rubbing on non-blistered skin can indeed cause a blister. Blister formation is a protective response of the body when outer layers of the skin, such as the epidermis, suffer trauma due to friction, burns, or infections. For example, the basal stem cells in the stratum basale of the skin are stimulated to divide more in response to constant friction, which can lead to callus formation or, under vigorous pressure, blisters. Blisters can also be symptomatic of various conditions such as contact with poison ivy, resulting in a hypersensitivity reaction, or as a result of infections like impetigo, which can cause blisters around the nose and mouth.
Other causes of blisters include viral infections, like the herpes virus causing cold sores, or physical damage such as overexposure to the sun leading to sunburn blisters. This indicates damage to the skin layers, specifically the epidermis and sometimes the upper dermis. Understanding the different mechanisms leading to blister formation—whether due to injury, skin diseases, or infections—helps in proper diagnosis and treatment.