A naturally occurring fungus called Malassezia globosa lives on every human scalp. Under normal conditions, it's completely harmless. But when it overgrows — triggered by excess oil, humidity, or a weakened immune response — it breaks down scalp oils into irritating byproducts.

Your scalp reacts by shedding skin cells at twice the normal rate. Those shed cells clump together and fall off as visible white or yellowish flakes.

Dry scalp and dandruff look similar but have opposite causes. A dry scalp lacks moisture — usually due to cold weather, hard water, excessive air conditioning, or over-washing. The flakes are typically smaller and whiter, and your scalp won't feel greasy.

Using a harsh anti-dandruff shampoo on a dry scalp can actually make things worse.

If your dandruff is yellowish, greasy, and accompanied by redness, you may have Seborrheic Dermatitis — a more advanced form of scalp inflammation. It's driven by overactive sebaceous glands producing too much oil, creating the perfect environment for Malassezia to thrive.

It can also affect the eyebrows, sides of the nose, and behind the ears.

What you eat shows up on your scalp. Deficiencies in Zinc, Vitamin B2, Vitamin B6, and Omega-3 fatty acids have all been linked to increased dandruff and scalp inflammation.

A diet high in refined sugar and processed foods can spike inflammation throughout the body — including your scalp.

Chronic stress doesn't directly cause dandruff, but it's a powerful amplifier. Elevated cortisol levels weaken your immune system, making it less capable of keeping fungal growth in check. Stress also disrupts hormonal balance, which in turn affects sebum production.

People often notice dandruff worsening during exams, deadlines, or emotionally difficult periods — this is exactly why.

There's a common misconception that washing more often reduces dandruff. In reality, overwashing strips your scalp of its natural protective oils — causing it to overproduce oil to compensate, worsening the dandruff cycle.

Shampoos with harsh sulfates, artificial fragrances, or alcohol can also irritate and inflame a sensitive scalp.

Hormones play a direct role in how much oil your scalp produces. This is why dandruff is particularly common during puberty, pregnancy, and periods of hormonal imbalance such as thyroid disorders or PCOS.

Men tend to experience dandruff more frequently than women — largely due to higher androgen levels that stimulate sebum production.