Scratching is a direct aggravating factor for AD skin lesions. An itch-scratch cycle (Fig. 24.2) develops, such that even after the elimination of other aggravating factors, the cycle can be a significant contributor to the continuation of skin rashes. There are various mechanisms of itching in AD, and it can involve histamine, non-histamine chemical mediators, direct stimulation of nerve fibers in the epidermis, involvement of the opioid system, neurogenic inflammation, and the effect of allergic inflammation. Since these mechanisms can combine to cause itching, it is necessary to comprehensively treat the patient with sufficient understanding of these mechanisms.

There are a range of bacteria and fungi that can become aggravating factors. There is a two-sided link between infections and AD: (1) in the area of an AD rash, the skin’s barrier function (including antibacterial peptide reduction [17]) is decreased and can become the site of an infection; (2) an immune response abnormality caused by an infection can alter the development and status of AD. Fungi such as Candida in the digestive tract or Malassezia on the skin have also been regarded as aggravating factors. This is owing to the fact that IgE antibodies against fungi are detected at a high frequency in patients with AD. In particular, in patients with severe symptoms on the head, face, and neck, it is said that specific IgE antibodies against Malassezia appear in high numbers. Furthermore, there is evidence that some patients with AD experience symptom alleviation with antifungal agents, supporting the idea that there is a link between fungal antigens and AD [18, 19].

Aggravation due to psychological stress is often seen in daily clinical practice. The stressors vary between age groups, and it is important to treat them appropriately so that the stress is effectively eliminated. Patients with AD have a two-phase distribution: the initial childhood phase, with a later peak around the age of 18 years. Therefore, it is logical that aggravating factors at this time include the stresses of university entrance exams, with associated sleep deprivation and chronic fatigue [20]. It is not yet sufficiently clear how stress becomes an aggravating factor for patients with AD. One theory states that a stress-scratch cycle (Fig. 24.3) develops, in which a psychogenic reaction occurs at times of stress, leading to addictive scratching and skin aggravation; this is followed by a sensation of itchiness in the aggravated skin, with more scratching and aggravation leading to further stress [21, 22]. This abnormal scratching is a type of behavioral abnormality induced by a psychological/social burden; in that situation, a psychiatric approach may be important.

Contact dermatitis is divided into allergic contact dermatitis, which occurs after sensitization, and primary irritation contact dermatitis, which can occur in anyone, depending on irritant concentration. Patients with AD are susceptible to both types of contact dermatitis, due to the decreased skin barrier function and long-term continuous use of topical applications. If any of the topical drugs used in AD treatment (steroids, nonsteroidal drugs, moisturizers, etc.) are used long term, contact dermatitis can develop [23, 24]. In addition, contact dermatitis is also not uncommon with use of home remedies, topical Chinese medicines, cosmetics, etc. If AD becomes aggravated, it is necessary to suspect the complication of contact dermatitis caused by these types of topical agents. For diagnosis, it is vital to perform a patch test to identify and eliminate the causative substance.

The skin of patients with AD is, for the reasons stated above, susceptible to increased dryness and itchiness, because of exposure to stimulating substances in daily life (dishwashing liquid, residual laundry detergent on clothing, chlorine for disinfection in pools, nylon or wool clothing, etc.). It is best to avoid tight-fitting or poorly ventilated clothing, stiff fabrics, and mechanical stimuli such as poor stitching and to choose soft fabrics such as cotton and silk [25]. Since the rise in pH after the use of soap impairs the barrier function, it is best to use mild or alkaline soaps and to avoid over-washing the body or hair. In the epidemiology of AD in Tibet, bathing was performed twice a month, and there was no AD onset [26].

Here, we outline the points from our surveys of physicians, patients, and pharmacists on the instructions provided to patients with AD for topical management: