Home / Hair Loss Treatments / Hair Fibers / Concealers / ProTHIK Spray ProTHIK Spray Prothik is a serious effective aerosol hair thickening system that cosmetically eliminates bald spots. Prothik is extremely effective during transitional “Grow-out” phases, between sessions and after completed procedures. Guarantee: They offer a risk free trial. No questions asked refund to your credit card for 4 weeks! If you don’t love it, you don’t pay. Price: $29.95 (plus $7.50 S&H)/ two bottles Availability: Online at .