Hair Loss, Dandruff & Nails: A Dermatologist's Guide
Hair and nails are part of the skin, and they often show changes first. Here is what helps with thinning hair, dandruff and oily scalps, and which nail changes deserve a closer look.
Written and medically reviewed by Dr. Danny Guo, MD, FRCPC, FAAD, board-certified dermatologist✓ Reviewed Nov 2026· 2 full videos · 16 Shorts
Key takeaways
- Losing about 50 to 100 hairs a day is normal. Gradual thinning, a widening part or sudden heavy shedding are worth checking.
- The cause of hair loss guides treatment, and approved regrowth treatments need several months of consistent use.
- Dandruff usually responds to medicated shampoos left on the scalp for a few minutes before rinsing.
- Many hair-growth products and supplements are expensive and poorly tested.
- A new dark streak in a nail, or a nail change that does not grow out, should be checked by a dermatologist.
What causes hair loss, and what helps?
Losing about 50 to 100 hairs a day is normal. The most common cause of thinning is pattern hair loss, which is inherited and gradually shrinks hair follicles. Sudden heavy shedding, often a few months after illness, surgery, childbirth, major stress or rapid weight loss, is usually temporary. Patchy loss, scalp pain or scaling point to other causes.
Because the cause guides treatment, it is worth seeing a dermatologist if hair loss is sudden, patchy or progressing. Blood tests for iron, thyroid function and other factors are sometimes needed.
Many hair-growth serums and supplements are expensive and poorly tested. Approved regrowth treatments, used consistently, have the best evidence, and results take at least three to six months to show. A dermatologist can also add prescription and in-clinic options.
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How do you treat dandruff and an oily scalp?
Dandruff and the more inflamed seborrheic dermatitis are linked to a yeast that lives on everyone's scalp. Medicated shampoos containing zinc pyrithione, selenium sulfide, salicylic acid or other anti-yeast ingredients help most people. Lather onto the scalp and leave on for about five minutes before rinsing.
Rotating between two medicated shampoos can help if one stops working. Once dandruff is under control, a medicated shampoo once or twice a week can keep it away.
An oily scalp is managed with regular washing. Washing more often does not make the scalp produce more oil, and skipping washes can let yeast and flakes build up.
What are the basics of healthy hair care?
Focus shampoo on the scalp and conditioner on the lengths and ends. Limit heat styling, frequent bleaching and tight hairstyles. Heat and bleach damage the hair shaft, and constant tension from tight styles can cause permanent hair loss over time.
Hard water can leave hair feeling dull, stiff and rough because minerals build up on the hair. A shower filter or an occasional clarifying shampoo can help.
Many hair rumours are not true. Plucking a grey hair does not make more grow back, and cutting hair does not make it grow faster. Once a hair has turned grey, it rarely regains its colour.
Which nail changes should you worry about?
Nail changes can come from injury, fungus, skin conditions like psoriasis or eczema, and sometimes from conditions elsewhere in the body. Not every thick or discoloured nail is a fungal infection, which is why testing before treatment is helpful.
A new dark streak running the length of a nail, especially one that is widening or spreading onto the surrounding skin, should always be checked by a dermatologist, because it can be a sign of melanoma.
Ingrown hairs are common after shaving or waxing. Shaving in the direction of hair growth, using a sharp blade and gentle exfoliation help prevent them. Plucking does not cause hair to grow back thicker.
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Frequently asked questions
How much hair loss is normal?
Losing about 50 to 100 hairs a day is normal. See a dermatologist if you notice clumps of hair coming out, a widening part, a receding hairline, bald patches, or shedding that lasts longer than a few months.
Do hair-growth supplements work?
Most hair supplements are poorly tested. They are unlikely to help unless you have a true deficiency, such as low iron, and high doses of some vitamins, like biotin, can interfere with lab tests. Ask your doctor before starting one.
How often should I wash my hair if I have dandruff?
Often enough to keep the scalp clean, which may be every day or every other day if your scalp is oily. Use a medicated shampoo two or three times a week, leaving it on for about five minutes, until flakes are under control.
Does stress cause hair loss?
Yes. A major physical or emotional stress can trigger heavy shedding, called telogen effluvium, usually two to three months later. It is usually temporary, and hair tends to regrow over six to nine months once the trigger has passed.
When should I see a dermatologist about my nails?
See a dermatologist for a new or changing dark streak in a nail, a nail that lifts, thickens or changes colour without an obvious cause, pain or swelling around the nail, or any change that does not grow out over a few months.
When to see a dermatologist
See a dermatologist for sudden or patchy hair loss, a scalp that is painful or scarring, or any new dark streak, lifting or change in a nail that does not grow out.
In Calgary?
Dr. Guo sees patients at Rejuvenation Dermatology. Learn more at calgaryderm.com.
Sources
Educational content only. It is not medical advice and does not replace an assessment by your own doctor or dermatologist.
