Which type of alopecia is considered the most extensive, involving hair loss across the entire body?

Alopecia universalis is characterized by the most extensive hair loss, affecting not just the scalp but also the entire body, including areas typically covered with hair such as the eyebrows, eyelashes, and body hair. This condition is an advanced form of alopecia areata, which involves patchy hair loss, but universalis encompasses a total loss of hair across all regions.

Alopecia totalis specifically refers to total loss of hair on the scalp only, making it less extensive than universalis. Alopecia areata can cause unpredictable patches of hair loss but does not result in complete body hair loss. Androgenetic alopecia, often referred to as male or female pattern baldness, typically affects only the scalp and is related to genetic and hormonal factors rather than autoimmune responses, distinguishing it further from the comprehensive nature of universalis.