to shampoos (and hair dyes) manifest with itching, redness of skin and is known as contact dermatitis
. Simply losing hair from specific areas (such as eyebrow or eyelash) is not a sign of contact dermatitis (also know as delayed hypersensitivity
It is also unusual to develop this at this age.
Chemical hypersensitivities are checked using patch tests that must be discussed with your dermatologist
Systemic disorders such as thyroid abnormality, lupus (with the screening ANA test), other features such as weight loss or eating disorders (such as anorexia nervosa
) need to be considered if they are relevant. Please discuss these with your doctor.
Blood tests such as complete hemogram, VitB12, folate, iron levels, ANA, LFTs, TSH fT4 are minimum investigations to exclude systemic disorders.
I hope that was useful.