What could be causing the browning of previously black hair on the hands of a patient with a history of androgenetic alopecia and seborrheic dermatitis?

Hair Color Change on Hands

The browning of previously black hair on your hands is most likely due to phototherapy exposure (particularly narrowband UVB treatment), nutritional deficiencies, or hormonal changes related to your underlying conditions, rather than a primary manifestation of androgenetic alopecia or seborrheic dermatitis themselves.

Primary Causes to Consider

Phototherapy-Related Pigment Changes

• Narrowband UVB phototherapy, commonly used to treat seborrheic dermatitis, can cause hair color changes including lightening or browning of hair 1
• This occurs through melanocyte stimulation and altered melanin production in hair follicles exposed to UV radiation 1
• If you have received any UV-based treatments for your seborrheic dermatitis, this is the most likely explanation 1

Nutritional Deficiencies

• Iron deficiency (low ferritin) is strongly associated with hair changes and occurs in 42% of patients with hair disorders 2
• Vitamin D deficiency affects 70% of patients with alopecia areata and can alter hair follicle function, potentially affecting pigmentation 2, 3
• Zinc deficiency impairs hair follicle function and may contribute to hair color changes 2, 3
• Folate deficiency may also contribute to hair abnormalities 2

Hormonal Factors

• In androgenetic alopecia, hormonal imbalances can affect hair follicle metabolism, potentially altering melanin production 4
• Free testosterone elevation (found in 52% of women with androgenetic alopecia) and other hormonal changes can affect hair pigmentation 4
• Thyroid dysfunction (TSH abnormalities in 20.8% of hair loss patients) can cause hair color changes 4

Diagnostic Approach

Laboratory Testing Priority

• Check serum ferritin first, as iron deficiency is the most common nutritional deficiency worldwide and affects hair pigmentation 2
• Measure vitamin D levels (deficiency defined as <20 ng/mL or <50 nmol/L) 2
• Assess serum zinc levels, particularly if you have resistant disease >6 months duration 2
• Check TSH to rule out thyroid disease 2, 4
• Consider free testosterone and SHBG if signs of androgen excess are present 4

Clinical History to Obtain

• Document any history of UV phototherapy or PUVA treatment for seborrheic dermatitis 1
• Review all current medications, as certain drugs can affect hair pigmentation 2
• Assess for other signs of nutritional deficiency (fatigue, brittle nails, skin changes) 2

Management Algorithm

If Phototherapy-Related

• Discuss with your dermatologist about adjusting UV exposure or using protective measures during treatment 1
• Hair color changes from phototherapy may be reversible after discontinuation 1

If Nutritional Deficiency Identified

• Supplement vitamin D if levels <20 ng/mL according to general international recommendations 2, 3
• Provide iron supplementation when ferritin is low, as this causes chronic hair changes 3
• Consider zinc supplementation if deficient, particularly in resistant cases 2

If Hormonal Imbalance Present

• Address underlying hormonal abnormalities with appropriate therapy to normalize the estrogen-androgen balance 4
• This may include low-dose antiandrogens or other hormonal treatments depending on specific findings 4

Important Caveats

• Seborrheic dermatitis itself can cause sebaceous gland atrophy, which may complicate hair follicle function and potentially affect pigmentation 5
• The combination of androgenetic alopecia and seborrheic dermatitis creates a complex inflammatory environment that may alter normal hair follicle cycling and melanin production 5, 6
• Hair color changes are not a typical primary feature of either androgenetic alopecia or seborrheic dermatitis alone, suggesting an external factor or nutritional deficiency is more likely 2, 3
• If diagnosis remains uncertain after initial workup, consider dermoscopy examination of affected hairs to assess follicular changes 2