Hair color changes

Hair color (see below hair, color changes) is determined by melanin and physical factors. There are 3 known melanin classes:

• Eumelanin
• Pheomelanin
• Neuromelanin.

Decisive for the hair colour are the black-brown eumelanins, which are formed by enzymatic oxidation of tyrosine, and the red-brown phaeomelanins, which are formed by reaction with cysteine. Hair of red-haired people contains trichromes, which can be assigned to the phaeomelanins. In a large European genome-wide association study (Hysi et al. 2018) 123 autosomal loci and a single X-linked locus were found in 300,000 participants, which are significantly related to hair color. The single nucleotide polymorphisms associated with hair colour explain the heritability of hair colour:

• 34.6% red hair
• 24,8% blond hair
• 26.1% black hair

Changes in hair color due to various endogenous/exogenous causes (varied n. H. Wolff 2018).

Metabolic disorders

• Phenylketonuria
• Homocystinuria
• Pernicious anemia
• Iron deficiency
• Vitamin A deficiency
• Copper deficiency (can lead to achromotrichia, as copper is a crucial trace element for tyrosinase)
• Copper deficiency in Menkes syndrome

Nutritive disorders

• Kwashiorkor (permanent protein deficiency leads to brown-red discoloration of black hair. Further to the bleaching of brown hair
• Intermittent protein deficiency e.g. in ulcerative colitis or after extensive intestinal resections (alternating dark and light stripes of the hair shaft, depending on the duration of the deficiency state - flag sign)

Exogenous factors

• Strong sun exposure (possibly in combination with salt water) on natural hair leads to fading of hair color (except black hair).
• Strong sun exposure (possibly in combination with salt water) on dyed or tinted hair leads to lighter shades of the originally chosen artificial colour.
• Copper: Copper dissolved in water (mostly in chlorinated swimming pools or from old water pipes) can lead to greening of the hair (especially with light hair). Ketchup (15 minutes under occlusion) can serve as a proven home remedy.

Medications:

• Dithranol leads to yellowing of the hair.
• Latanaprost: may lead to repigmentation of white hair on the head
• Benzoyl peroxide (bleaching of the hair)
• Tetracyclines (yellowing)
• Hydroxychloroquine (storage in the hair shaft, hair can become white/silver)
• Dizaoxid, Minoxidil (hair becomes darker)
• Carbidopa, Bromocriptine (white hair becomes darker)
• Mephesine, triparanol, butyrophenone, haloperidol, bleomycin (reversible pigment loss, hair may prematurely turn gray)

Graying due to disturbance of melanin synthesis

• Canities: Hair consists of more than 80% alpha-keratin, a fibrous protein. Keratins are colourless per se. The color of the hair shaft is defined by melanin, which is formed in the follicular matrix by a series of oxidation steps from the amino acid tyrosine. In gray hair, melanin is reduced or completely absent in the hair shaft. Instead, tiny air bubbles (vacuoles) are formed during keratin synthesis, which, embedded in the hair shaft, define the shade of gray or completely white hair.
• Canities (acute graying, premature graying)
• Canities caused by chemotherapeutic agents: can lead to a faster graying of the hair.
• Canities caused by EGF receptor blockers: cyclic administration may lead to stripe-like (zebra pattern) discolouration. During the pause in therapy, the hair continues to grow with its natural colour.
• Albinism
• Poliosis
• Piebaldism
• Cri-du-chat syndrome

Other

• Air bubble hair (hair shaft abnormality due to inclusions of irregularly sized air bubbles in the hair shaft.
• Autosomal recessive inherited woolly hair (often white blond hair)
• Pili anulati (alternating light and dark bands due to air inclusions)

1. Savitha A et al (2011) Bubble hair and other acquired hair shaft anomalies due to hot ironing on wet hair. Int J Trichology 3:118-120. https://www.ncbi.nlm.nih.gov/pubmed/22223976
2. Wolf H (2018) Hair diseases. In: G. Plewig et al (Ed.) Braun-Falco`s Dermatology, Venerology and Allergology, Springer Reference Medicine S1361-1363