2. Chinese medicine believes that hair refers to foods that are nutritious or irritating, and are particularly prone to induce or aggravate certain diseases (especially old diseases), while bracken is sweet and astringent in taste, cold in nature, and covered with fine hair, which can be eaten by ordinary people in moderation, but some people can easily induce allergic diseases after eating, such as urticaria, eczema, dermatitis and other skin diseases or respiratory diseases such as asthma, cough and itching.