Not every type of Alopecia is Contagious...
Alopecia can be divided in 2 big categories: Non-Scarring
Alopecia (the most common) and Scarring Alopecia.
One of the subtypes of Scarring Alopecia is Infectious Alopecia
and can be produced by several agents: fungal (Kerion, candidiasis,
favus, tinea corporis), bacterial (syphilis, leprosy, acne
necrotic) viral (herpes, varicella); protozoa (Leishmaniasis).
It is important to recognise though that this condition is quite
uncommon these days.
Alopecia is hardly ever due to an infection and is therefore,
generally speaking, not a contagious condition.