While “excessive testosterone” shouldn’t sound like a reason for men to worry, it is a well-known and proven truth that DHT (dihydrotestosterone, synthesized from testosterone) blocks nutrient supply to the hair follicles, leading to progressive hair thinning. As a consequence of this blockage, roots are not properly nourished, which will first reflect in the appearance of the hair shaft and then the width will miniaturize. According to a study conducted by the University of Jena in Germany, caffeine can penetrate hair roots, protecting them from DHT and preventing hair loss. A new study conducted by the Berlin university clinic shows the average time for the caffeine formula to reach hair roots and take effect is about 120 seconds. For that reason, caffeine shampoos are frequently used in the treatment of alopecia areata, although the final result depends on each person’s body and the way it reacts to the use of these products. There isn’t any conclusive scientific evidence to either support or disprove the effectiveness of caffeine shampoo on a large scale.