Structural Differences in Black and Caucasian Skin
- Same number of melanin producing cells per unit surface area but more effective production of melanin in Blacks.
- Increased collagen production, a genetic condition found also in whites but more commonly in blacks, results in prominent scars and keloids.
- No differences in sweat or sebaceous gland activity (but less acne of severe nodular cystic type in Blacks).
Reaction Pattern Differences
Major differences in reaction patterns of Black skin to illness, inflammation, trauma. All reaction patterns are prominent and often exaggerated.
- Follicular: small papules around hair follicles, often diffuse. Seen in eczema, scarlet fever.
- Annular lesions: nummular eczema, secondary syphilis.
- Lichenification: chronic eczema, often becomes hyperpigmented.
- Keloid formation: scars.
- Ulcerative reactions: prominent in SS anemia, lupus, chicken pox.
- Vesiculobullous reactions very common in children: insect bites, chicken pox.
- Granulomatous reactions: sarcoid.
Inflammation, trauma and medications used for topical treatments often result in hypopigmentation or hyperpigmentation. Post inflammatory hyperpigmentation is due to deeper dermal inflammation (impetigo, chicken pox, herpes, acne) and resolves very slowly over years. It is often permanent. Most superficial dermatitis results in hypopigmentary conditions that tend to improve with time and may respond to non-fluorinated topical steroids.
- Congenital hypopigmentation, usually midline, is common. Futcher’s lines of hyperpigmentation on arms, legs. Mongoloid spots.
- Vitiligo is a major cosmetic problem, noted earlier in pigmented skin. (2% incidence is same in whites and blacks.)
- Post inflammatory hypopigmentation commonly seen with superficial dermatitis such as seborrheic dermatitis, diaper dermatitis, pityriasis alba on face in children. Resolves over time with sun light exposure and 1% hydrocortisone.
- Scratching and secondary infection produce hyperpigmentation in eczema, pityriasis rosea and chicken pox. Treat aggressively and early to prevent itching and infection.
- Medications commonly cause pigment changes:
- fluorinated steroids cause hypopigmentation.
- retin A can produce inflammation and hyperpigmentation acutely but lightens skin over time.
- benzoyl peroxide is bleaching agent and can cause loss of pigment (topical antibiotic solutions usually well tolerated for acne treatment).
- Miliaria and papular eruptions from occlusive oils/vaseline, hair oils and softeners, pomade acne.
- Use of bleaching creams is common in African Americans and West Africans
- Hair straighteners commonly cause chemical dermatitis and burns.
- Visits to the Southeast US are associated with infected insect bites, impetigo, tinea versicolor in children.
- Traumatic alopecia and folliculitis from corn rowing, tight hair braids or tufts.
- Traditional cosmetic practices: tattoos, henna on fingernails/toenails, scarification.
- Traditional healing practices: Coining causes linear purpuric/petechial lesions on back and chest in SE Asians. Circular burns used to treat severe febrile illness and hepatitis in E. Africa – burn scars are located periumbilical, wrists, ankles.
Neonatal and Infant Dermatoses
- Transient neonatal pustular melanosis – lesions seen at birth to 48 hrs in 4%-5% of AA newborns and can be confused with herpes. Herpes vesicles are on an erythematous base and usually clustered. The lesions of TNPM are scattered and on a pigmented macule. TNPM leaves a hyperpigmented macule that fades with time (3 weeks to 3 months).
- Acropustulosis of Infancy – Pustules on distal extremities, palms and soles predominantly in black male infants in 1st 1-2 years of life. Lesions are intensely pruritic and recur. Often confused with scabies. Antihistamines give some relief. Dapsone 2 mg/kd/day is recommended for severe cases. (Need to check for G6PD deficiency before treating.)
- Tinea capitis is very common in Blacks and is due to trichophyton tonsurans. Any area of alopecia with scaling (even slight) is tinea in a Black child and needs treatment with griseofulvin 15-20 mg/kg/day x 4-6 weeks. Selenium sulfide shampoo helps prevent spread of spores in household. Antibiotics not needed even though looks pustular. Short course of steroids (1-2 mg/kg x 5 days), wet to dry compresses help resolve a painful kerion. There is a high prevalence (45-63%) of asymptomatic or previously unnoticed clinically cases of tinea capitis in the household of an index case. Use selenium sulfide (2 1/2 %) shampoo in all household members and suggest careful inspection of their scalps by a parent.
- Pityriasis alba (may be low grade variant of atopic dermatitis)- Slightly scaling hypopigmented macules on cheeks.
- Lichen nitidus — grouped, hypopigmented or hyperpigmented, flat topped papules on extremeties, trunk. Resolve slowly over months.
- Papular urticaria secondary to flea and insect bites…lesions result of blood-borne antigens to which body develops immune complexes.
- Pityriasis Rosea may have inverse distribution – more on face, neck, axillae and extremities, than on the trunk. Lesions are often patches of small papules with scattered follicular papules on extremeties and may not appear erythematous.
- Non-specific confluent follicular eruptions involving the head and upper chest are very common in AA children. There is usually no fever or pharyngitis and throat cultures are negative for strep. The rash resolves spontaneously after several days. Diphenhydramine helps if there is pruritis.
- Acne less common and severe in Blacks but causes more permanent hyperpigmented macules. Recent study, NEJM 327 , 5/20/93, 1438-1443, found significant improvement in hyperpigmentation with 0.1% retinoic acid cream applied nightly for 40 weeks.
- Men who shave closely develop ingrown hair in beards. This also causes significant facial hyperpigmentation. Recommend “magic shaving powders” (a depilatory) and use of electric razors. Shave infrequently.