7.1 Hair & Scalp Diseases and Disorders
Key Takeaways
- Hair shaft disorders like trichorrhexis nodosa, monilethrix, and canities are non-contagious structural or genetic conditions, so you may still service the client, often with gentler handling
- Alopecia (hair loss) has several forms, including areata, androgenic, totalis, and universalis, and all are non-contagious and safe to service since there is no infectious agent involved
- Tinea capitis (ringworm) and pediculosis capitis (head lice) are contagious and require refusing service and referring the client to a physician
- Furuncles (boils) and carbuncles are bacterial scalp infections that must be avoided entirely until treated, even though the surrounding scalp may otherwise be serviceable
- The core PSI theory question for every scalp finding is the same: identify the condition, decide whether it is contagious or actively infected, then choose proceed, modify, or refer
Hair & Scalp Diseases and Disorders
Quick Answer: A disorder is a non-contagious abnormality of hair structure, growth, texture, or color, so you may still service the client, sometimes with gentler handling. A disease of the scalp caused by a fungus, parasite, or bacterium is contagious or actively infectious, which means you must refuse the service and refer the client to a physician.
Domain 2 of the Michigan PSI National Cosmetology Theory exam (Client Consultation and Hair, Skin, and Nail Analysis) rarely asks you to simply name a condition. It asks you to recognize a description and choose the correct action: proceed, modify, or refer. That decision almost always comes down to one question: is a living pathogen present?
Hair Shaft Disorders (Non-Contagious)
These conditions change the structure, growth pattern, or pigment of the hair itself. None are caused by a pathogen, so none require refusing service, though several call for gentler handling to avoid worsening breakage.
| Disorder | Description | Typical Cause | Service Decision |
|---|---|---|---|
| Trichoptilosis | Split ends; longitudinal splitting of the hair shaft | Mechanical or chemical damage, dryness | Proceed, trim off the damaged ends |
| Trichorrhexis nodosa | Nodes or swellings along the shaft; hair snaps at the nodes | Heat, chemical, or mechanical damage | Proceed with gentle detangling; avoid aggressive brushing |
| Monilethrix | Beaded appearance; shaft narrows at regular intervals and breaks at the thin points | Hereditary keratinization defect | Proceed with gentle handling; limit harsh chemical services |
| Canities | Gray or white hair from loss of melanin | Congenital (rare) or age-related (common) | Proceed; purely cosmetic |
| Hypertrichosis | Excessive hair growth in areas not typically hairy | Hormonal, hereditary, or medication-related | Proceed with requested removal or styling service |
| Fragilitas crinium | Brittle hair that splits easily | Chemical over-processing, dryness | Proceed; recommend reconstructive treatments |
Alopecia: Hair Loss Is a Disorder, Not a Disease
Alopecia simply means hair loss, and none of its forms are contagious, so all are safe to service.
| Type | Presentation | Cause | Service Decision |
|---|---|---|---|
| Alopecia areata | Sudden, patchy, well-defined bald spots | Autoimmune | Proceed; camouflage or styling services are appropriate |
| Androgenic alopecia | Gradual thinning, receding hairline, or crown loss | Genetics and hormones | Proceed; common in both men and women |
| Alopecia totalis | Complete loss of scalp hair | Autoimmune, advanced | Proceed; wig or hairpiece consultation is appropriate |
| Alopecia universalis | Complete loss of hair on the entire body | Autoimmune, advanced | Proceed; no infectious risk to the stylist or other clients |
Contagious Scalp Diseases: Refuse and Refer
These conditions involve a living pathogen that can spread through combs, brushes, linens, or direct contact. A cosmetologist must never service an active case.
| Disease | Cause | Key Signs | Action |
|---|---|---|---|
| Tinea capitis (ringworm of the scalp) | Fungal | Round, red, scaly patches; broken hairs; possible hair loss | Refuse service; refer to a physician |
| Pediculosis capitis (head lice) | Parasitic (insect) | Visible lice or nits, intense itching | Refuse service; refer for medical or pharmacy treatment |
| Scabies | Parasitic (mite) | Intense itching, burrow-like tracks on skin near the hairline | Refuse service; refer to a physician |
Non-Contagious Scalp Conditions: Proceed with Caution
These findings are common and not infectious, but several still change what you should do.
| Condition | Cause | Notes | Service Decision |
|---|---|---|---|
| Seborrheic dermatitis (dandruff) | Overactive sebaceous glands, yeast overgrowth | Flaking, sometimes redness or itching | Proceed; recommend clarifying or medicated shampoos |
| Psoriasis (scalp) | Autoimmune; skin cells build up too fast | Thick, silvery-white scaly patches | Proceed if skin is intact; avoid scratching or irritating patches; refer if bleeding or cracked |
| Folliculitis | Bacterial infection of hair follicles | Small, tender, red pustules | Proceed if very mild and isolated; refer if widespread, painful, or draining |
| Furuncle (boil) / carbuncle | Deeper bacterial infection, often Staphylococcus | Painful, swollen, pus-filled lump(s) | Do not service the area; refer to a physician until fully healed |
Sanitation Connects Every Scalp Finding
Even when a scalp condition is non-contagious, tools that touch the scalp must still be cleaned and disinfected between every client, because you cannot always be certain of a diagnosis by sight alone. This is why the exam pairs Domain 2 disease-and-disorder knowledge so closely with Domain 1 infection control: proper implement disinfection is the safety net that protects the next client even when your visual assessment turns out to be wrong.
The Three-Step Decision Framework
For every hair or scalp finding on the PSI exam, apply the same framework:
- Identify — Is this a structural or growth disorder, or a disease with a pathogen?
- Assess — Is it contagious, actively infected, or inflamed and open?
- Decide — Proceed as normal, proceed with modification, or refuse and refer.
Memorize the pattern rather than every disorder name in isolation: hair shaft disorders and alopecia are always safe to service because there is no pathogen; fungal and parasitic scalp diseases always require refusal because they spread; bacterial scalp infections require refusal only while active and untreated. Document whatever you observe and whatever action you take on the client's consultation card, both to protect the client and to protect your license.
Which hair shaft disorder is characterized by hair that breaks at regularly spaced nodes and has a beaded appearance under magnification?
A client has round, scaly, red patches on the scalp with some broken hairs within the patches, and no lice or nits are visible. What is the most likely condition and correct action?
Which of the following scalp conditions should generally be serviced with caution rather than refused outright, because it is not contagious even though it can look alarming?