Can low complement levels cause lichen planus ( armpit) and tinea versicolor?

No: Low complement levels in the blood are associated with some hives with blood vessel inflammation called hypocomplementemic urticarial vasculitis and with recurrent infections with Meningococcal infections. To avoid a falsely low complement level, the blood sample has to be processed in the lab quickly.

Yes and no: Tinea versicolor is a fungal infection. It may present due to a decrease in the immune system (low complement). Lichen planus is an autoimmune disorder of unknown origin. Various autoimmune illnesses are associated with increased incidence in lichen planus. Secondary raynaud's disease also has been linked with some autoinmune disorders such as lupus, rheumatoid arthritis and sjogren's syndrome.