Many children are misdiagnosed with head lice when they exhibit symptoms of piedra because they are unsure how to differentiate between the two. However, both causes and symptoms are very different. While trichomycosis nodularis is caused by a fungal infection, head lice is caused by an infestation of parasitic lice, which are roughly the size of a sesame seed. The most prominent symptom of head lice is itching, which is really an allergic reaction to certain toxins transferred to your blood when lice puncture the skin. On the other hand, symptoms of trichomycosis nodularis often go unnoticed because the most prominent symptom is the presence of hardened nodules in your hair. Similarly, while head lice can be treated with insecticidal lotions or shampoo, piedra can be treated with antifungal medicine.