Investigation of possible relationship between atopic dermatitis and salivary biomarkers, stress, and sleep disorders

Table 1 Atopic dermatitis and salivary biomarkers

Salivary biomarker	Specifications	Effect on atopic dermatitis	Ref.
Cortisol	Activates the metabolism, after physical or psychological stress, which supplies the body with energy and changes the conditions for mental reactions, increasing the action of other hormones and generating additional energy stimuli to cope with stressful situations	Salivary cortisol level may be a useful biomarker to assess stress in patients with AD. Patients with AD may present elevated cortisol	[4,18,25]
Chromogranin A	Reflects catecholamine secretion in the blood and functions as a marker of sympathetic adrenomedullary system activity	Severe AD is associated with elevated stress levels and salivary measurements of chromogranin A may be useful as a marker in the objective investigation of stress. In the most severe cases of AD, the chromogranin A levels in saliva were higher	[28,29]
Alpha-amylase	Digestive enzyme and a biomarker of the autonomic nervous system. Both sympathetic and parasympathetic nervous system innervations stimulate salivary alpha-amylase secretion via α- and β-adrenergic mechanisms	Salivary alpha-amylase activity increases in individuals with chronic psychosocial stress and can be used as a biomarker of chronic stress	[31,33,36]
Melatonin	Hormone with a function in sleep regulation. The literature suggests that melatonin has immunomodulatory, anti-inflammatory, and antioxidant effects and may improve skin inflammation and help to maintain a functional epidermal barrier in patients with AD	Decreased nocturnal secretion is associated with sleep disturbances and greater AD severity in children. It has been shown that salivary melatonin levels are reduced in patients with AD. In parallel, melatonin production is reduced by stress	[8]
IgA	Plays a role in defence against bacteria and viruses. IgA may help to prevent the development of allergic inflammatory reactions, and IgA deficiency could promote allergic sensitization and also be a marker of stress	Low serum IgA levels have been related to AD severity	[23,40,43,45]

AD: Atopic dermatitis; IgA: Immunoglobulin A.