That said, any styling ritual that consists of intense heat and harsh chemicals on your scalp and hair—using curling and flat irons, getting frequent perms, chemical straightening procedures, or relaxing treatments—can damage the follicle, and worst case scenario, cause permanent hair loss.
What you’ll probably notice
Trichorrhexis nodosa usually involves a combination of hair loss and changes in texture: Your hair might look frayed, with small, bead-like nodes along the strands, and feel brittle to the touch.10 “You may also notice increased breakage, and shorter, uneven strands,” Dr. Mitchell says. “In more severe cases, there might be patches of thinning or an overall reduction in hair density.”
5. Severe dandruff
There’s dandruff and then there’s its more severe cousin, seborrheic dermatitis: A pesky skin condition characterized by a rash (that may look darker, lighter, or redder than the surrounding skin), as well as itchy and flaky patches that set up shop in spots with a lot of oil glands, including your scalp. “It’s driven by an inflammatory response against organisms that live on our scalp—specifically, Malassezia yeast colonies,” Dr. Lo Sicco says.11
These flaky patches, combined with the oil that’s produced by the scalp, can clog your follicles, ultimately impairing the hair’s nutrient supply and weakening its structure (not to mention the subsequent damage—and shedding—that can happen when you constantly scratch your head).12 Meanwhile, the inflammatory response disrupts the normal hair growth cycle and can trigger telogen effluvium, Dr. Mitchell explains, where, again, your hair follicles go on strike for an extended period, only to later shed in bulk.
What you’ll probably notice
Aside from the whole inflamed scalp thing, this type of hair loss isn’t usually associated with dramatic balding, but a gradual reduction in hair density—particularly in the form of increased shedding wherever the seborrheic dermatitis is giving you the most trouble. “The hair itself may also become finer and more fragile due to the inflammatory processes disrupting the growth cycle,” Dr. Mitchell says.
6. Inflamed hair follicles
Folliculitis is a skin condition that strikes when hair follicles become inflamed—say, from physical irritation (shaving, traction, wigs) or an infection (bacterial, fungal)—which compromises the integrity of the follicles.13
There are two main types of folliculitis: superficial and deep. The former involves only part of the hair follicle and will likely heal within a few days, whereas the latter consumes the entire follicle and tends to be more severe and long-lasting.
“As the follicle becomes inflamed, damage can happen to the surrounding tissues that disrupt the normal hair growth cycle,” Dr. Mitchell says. “In severe cases, the infection may lead to scarring, causing permanent hair loss.”
What you’ll probably notice
The particular type of folliculitis you experience will depend on the underlying cause (friction or infection), but “it typically presents as small, acne-like bumps or pustules surrounding the affected hair follicles,” Dr. Mitchell says. “These may be itchy, tender or painful, and in some cases, form clusters that resemble a rash.” As the condition progresses, you might start noticing the surrounding skin becoming irritated and darker, lighter, or redder, too.