What Are Hair Casts? Causes, Triggers & Treatment
Have you ever noticed tiny white or translucent tubes that slide along the hair shaft and wondered what they are? These are called hair casts, and while they’re often mistaken for lice eggs (nits), they’re actually quite different, and much more common than you might think.
At Halo Haircare Society, we specialise in hair and scalp health, so let’s take a closer look at the science behind hair casts, why they occur, who is more likely to get them, and how to treat them.
What Exactly Are Hair Casts?
Hair casts, also called pseudonits, are cylindrical, keratin-based sheaths that form around the hair shaft. Unlike lice eggs, hair casts aren’t stuck in place, they can move freely up and down the hair strand.
These casts are made from keratin and remnants of the inner root sheath of the hair follicle. Normally, these inner layers disintegrate as the hair emerges from the scalp, but when this natural process is disrupted, those layers can stick around and form a cast.
Why Do Hair Casts Form?
There are two main types of hair casts, and they can have very different causes:
Primary Hair Casts
These occur without any underlying scalp condition. They’re often linked to:
- Tight hairstyles
- Heavy use of styling products or dry shampoos
- Excessive keratin production
- Oily scalps or infrequent washing
- Mechanical stress on the scalp or follicles
This type is more common in adolescents and young women.
Secondary Hair Casts
These are associated with inflammatory or infectious scalp conditions, such as:
- Seborrheic dermatitis
- Psoriasis
- Lichen planopilaris
- Discoid lupus erythematosus
- Tinea capitis (fungal infection)
- Folliculitis decalvans
- Traction alopecia
In these cases, hair casts are often more numerous and linked to inflammation around the follicle and abnormal keratinization.
Who’s More Likely to Develop Hair Casts?
Hair casts can affect anyone, but they’re more common in:
- Young females
- People with naturally oily scalps
- Those who frequently use dry shampoo or styling products
- Individuals with underlying scalp conditions
- People experiencing hair shedding or loss, such as telogen effluvium or alopecia areata
Internal or Systemic Triggers
Hair casts can also be influenced by what’s going on inside the body. Contributing factors include:
- Hormonal imbalances, especially androgens (which affect sebum and keratin production)
- Nutritional deficiencies, such as low zinc, vitamin A, and essential fatty acids
- Autoimmune conditions like lupus or psoriasis
- Chronic stress, which impacts the immune system and skin barrier
- Changes in the scalp microbiome
How Can You Treat Hair Casts?
For Primary Hair Casts (No Underlying Scalp Disease):
- Use gentle, non-occlusive shampoos to prevent buildup
- Avoid excessive dry shampoo, oils, and tight styles
- Incorporate scalp exfoliation using salicylic acid or mild mechanical exfoliants
- Condition and detangle before combing with a fine-toothed comb to slide casts off
- Maintain a healthy scalp barrier by avoiding overly stripping cleansers
For Secondary Hair Casts (Linked to Scalp Conditions):
- Treat the root cause: whether it’s inflammation, fungal infection, or an autoimmune process
- Use keratolytic agents like urea, lactic acid, or salicylic acid to reduce buildup
- Apply topical anti-inflammatories, such as corticosteroids or prescription treatments
- In some cases, oral medications or antimicrobials may be needed
- Trichological scalp treatments and low-level laser therapy (LLLT) may support healing and follicle health.
What Else Could It Be?
Hair casts are often confused with other conditions:
- Lice eggs (nits) – firmly stuck to the hair shaft and don’t slide
- Product residue – doesn’t form a full tube and washes off easily
- White piedra – a fungal infection with hard nodules
- Keratin plugs – seen in conditions like scalp psoriasis or keratosis pilaris
Final Thoughts
Hair casts might be harmless, but they can signal that your scalp needs a little extra attention. Whether you’re dealing with buildup, inflammation, or simply using too many styling products, hair casts are often your scalp’s way of telling you it’s time for a reset.
If you’re experiencing persistent hair casts, or if they’re accompanied by flaking, itching, or hair shedding, it’s a good idea to book a scalp consultation. As always, our trichologist is here to help you understand what your scalp needs to thrive.
Want to learn more about your hair and scalp health?
Check out our personalised blogs or get in touch for a 1:1 consultation.
