What causes dry skin and hair?

Causes of Dry Skin and Hair

Dry skin and hair result from a combination of environmental factors (low humidity, excessive bathing, harsh soaps), aging-related changes (decreased androgen hormones, reduced sebum production), systemic conditions (hypothyroidism, nutritional deficiencies), and medications (antihistamines, diuretics, retinoids) that disrupt the skin's barrier function and reduce moisture retention.

Environmental and Lifestyle Factors

Environmental triggers are the most common and modifiable causes:

• Low humidity environments from air conditioning, heating, or arid climates accelerate water evaporation from the skin surface 1, 2
• Excessive bathing and harsh soaps strip natural lipids from the skin, removing the protective barrier that prevents water loss 3, 4
• Direct air flow from fans or HVAC systems increases evaporative loss 2
• Extended screen time with reduced blink rate affects ocular surface moisture but reflects broader environmental stress patterns 1, 2

Age-Related and Hormonal Changes

Aging is a major non-modifiable risk factor:

• Decreased androgen hormones with aging reduce sebum production and compromise the skin's ability to maintain moisture 3
• Postmenopausal estrogen decline causes skin dryness, thinning, and reduced hair growth, with hormone replacement therapy (particularly estrogen alone) paradoxically increasing dry eye risk 3, 5
• Menopausal changes affect skin as an endocrine organ, causing dryness, pruritus, thinning, reduced hair density, and altered hair quality 5

Systemic Medical Conditions

Several underlying diseases must be ruled out:

• Hypothyroidism is a critical diagnosis to exclude, as it commonly presents with dry skin and hair as prominent features 4
• Autoimmune conditions including Sjögren's syndrome (affecting exocrine glands), rheumatoid arthritis, and autoimmune thyroid disease cause systemic dryness 3, 1
• Diabetes mellitus, particularly with poor metabolic control, increases dry skin prevalence 3, 1
• Occult malignancy (carcinoma, lymphoma) can manifest as dry skin and warrants consideration in unexplained cases 4
• Renal or biliary disease may present with dry skin as an early finding 4

Medications

Multiple drug classes cause or exacerbate dryness:

• Antihistamines reduce tear and sebum production through anticholinergic effects 3, 1
• Antidepressants and antianxiety medications (including duloxetine/Cymbalta) disrupt moisture regulation 3, 1, 6
• Diuretics cause systemic dehydration affecting skin moisture 3, 1
• Systemic retinoids (isotretinoin for acne) significantly reduce sebum production and cause severe dryness 3, 1
• Anticholinergics disrupt efferent cholinergic nerves that stimulate secretion 3, 1
• Oral corticosteroids affect skin barrier function 3, 1

Nutritional Deficiencies

Specific nutrient deficits directly impact hair and skin health:

• Iron deficiency (even without anemia) causes increased hair shedding, with serum ferritin <70 μg/L being significant when ESR is normal 7
• L-lysine deficiency (essential amino acid) contributes to hair loss, and supplementation with iron shows benefit in double-blind studies 7
• Protein-energy malnutrition from starvation or eating disorders causes hair loss and skin changes 7
• Vitamin A deficiency affects skin integrity, though excessive supplementation paradoxically causes hair loss 1, 7

Important caveat: Low serum zinc does not cause hair loss despite popular belief, and excessive nutritional supplements may actually worsen hair loss 7

Pathophysiologic Mechanisms

Understanding the underlying dysfunction guides management:

• Skin requires 10-15% water content to remain supple; this includes both bound ("static") and free ("dynamic") water 8
• Intercellular lipid disruption compromises the barrier function, allowing increased transepidermal water loss 8
• Reduced sebum production from aging or hormonal changes decreases the hydrophobic protective layer 8, 4
• Inflammatory cascade can develop when barrier function is compromised, perpetuating dryness 3

Dermatologic Conditions

Specific skin diseases present with dryness:

• Atopic eczema features general dry skin as a diagnostic criterion, with visible flexural involvement 3
• Rosacea affects both skin and eyes, causing prominent sebaceous glands and exacerbating dryness 3, 1
• Ichthyosis and other keratinization disorders cause excessive scaling and dryness 3

Clinical Approach to Evaluation

When evaluating dry skin and hair, systematically assess:

• Medication review for causative agents (antihistamines, antidepressants, diuretics, retinoids) 3, 1
• Thyroid function testing to exclude hypothyroidism 4
• Iron studies including serum ferritin (target >70 μg/L with normal ESR) in patients with hair loss 7
• Environmental exposure history including bathing frequency, soap use, humidity levels, and occupational exposures 3, 8, 4
• Systemic disease screening for autoimmune conditions, diabetes, renal/hepatic disease, and malignancy in refractory cases 1, 4

Common pitfall: Patients often reduce shampooing frequency due to fear of hair loss, but this increases visible shedding during subsequent washes and adversely affects quality of life 7