The short answer
A dry scalp tends to give small, dry, white flakes and a tight feel. It is dry skin, the same as dry skin on your shins or hands. A few habits go a long way. If the flakes look different from that, ask your pharmacist before you add anything.
Why it happens
A scalp loses moisture when the air is cold or dry, when the water is very hot, when you wash often, or when a cleanser is harsh. It is more common in winter, when the air indoors and out is dry. A change in the products you use can make a scalp feel different too, so it is worth thinking back over the past few weeks.
What helps
Wash with lukewarm water rather than hot, and use a mild cleanser. Rinse well so nothing is left behind on the skin. Use the pads of your fingers when you wash, not your nails.
If your scalp feels tight between washes, a small amount of a plain moisturizer along the parts can make it more comfortable. Go lightly, because too much just sits there and makes the next wash harder.
A few small things help too. Keep scarves and head wraps clean. Change pillowcases regularly. If you change a product, change one at a time so you can tell which one made the difference.
When to ask for help
See your pharmacist if the flakes are large, greasy or yellowish, or if they keep coming back. That usually calls for a different kind of product than a moisturizer, and a pharmacist can go through the options with you. Take the bottle or jar with you.
See your doctor if the scalp is red, sore or weeping, if it forms thick crusts or sores, or if there are patches that look different from the rest.
The AHOTO note
Golden and Pure Shea are for a dry, tight feeling scalp only, and they are cosmetic. Golden contains oats and soy, so patch test it first on the inside of your forearm.