sometimes it's because u don't wash your hair enough.
Dry scalp.
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If you do not wash your hair, your hair will get REALLY greasy and thin. It will get frizzy and staticky and you will look horrible. Also, you will get BIG painful pimples on your head preventing you from brushing your hair and your scalp will dry and flake.
The scalp could be red from rosacea or an allergy to shampoo.
Poor hygiene?
When your hair is relaxed and overprocessed.
Really anything, it can be caused by a food or a smell or also reading. Don't think it's your brain its actually the viens between your scalp that are swollen.
your scalp (the skin on the top of your head)
Dandruff is a fungus that grows on every ones scalp
Could be an insect bite.
Scalp sores can often result from an itchy flaky scalp, where skin is starting to scale and peel off. This, particularly if combined with shampoo that is irritating the scalp, can lead to needing to scratch one's scalp to alleviate this. In doing so, the scalp can become inflamed and lead to sores.
Dry scalp is an itchy and potentially embarrassing condition. it is caused by a variety of medical conditions as well as stress and weather changes.