Most scalp complaints are not infections. Itch, flaking, oiliness and tenderness usually trace back to seborrhoeic dermatitis, psoriasis, contact reactions or simple irritation. True infection is less common, and most cases fall into three families: fungal, bacterial, and viral.
The reason this matters is that the three families look different, behave differently, and need different treatment. Confusing one for another wastes time and sometimes makes things worse.
Fungal: tinea capitis and kerion
Tinea capitis is a fungal infection of the scalp caused by dermatophytes — most often Trichophyton and Microsporum species.1 It is predominantly a disease of children. Classic features are patchy hair loss with scale, broken hairs at the surface (“black dots”), and sometimes lymph nodes at the back of the neck.1
A kerion is the inflammatory form: a boggy, tender, pus-studded plaque that can be mistaken for a bacterial abscess.2 The pus is part of the immune response to the fungus, not a separate bacterial problem, and incising it does not help.
The point worth keeping is this: topical antifungal shampoos alone do not cure tinea capitis. Oral antifungal treatment is required, typically griseofulvin or terbinafine, for several weeks.3 Shampoos help reduce shedding of spores to household contacts but they do not reach the hair shaft itself.3
Bacterial: folliculitis, furuncles and impetigo
Bacterial scalp infections most commonly involve Staphylococcus aureus.4 Superficial folliculitis presents as small, tender, pus-tipped bumps around individual hair follicles. A furuncle (boil) is a deeper, more painful nodule. Impetigo, more common in children, shows honey-coloured crusts.5
Most superficial bacterial infections of the scalp respond to topical antibiotics and gentle cleansing.4 Deeper or recurrent infection, fever, or spreading redness warrants oral antibiotics and clinical assessment, particularly given the rise of methicillin-resistant strains.6
Two scalp-specific conditions deserve naming. Folliculitis decalvans is a chronic, scarring form of folliculitis that progressively destroys follicles and leaves smooth patches of permanent hair loss.7 Dissecting cellulitis of the scalp produces deep, interconnected nodules and sinus tracts, more common in young men, and is poorly responsive to simple antibiotics.8 Both are scarring, both need specialist care, and neither resolves with over-the-counter measures.
Viral: herpes simplex and herpes zoster
Viral infections of the scalp are uncommon but worth recognising. Herpes simplex can occur on the scalp, presenting as grouped vesicles on a red base, often painful or tingling before the rash appears.9
Herpes zoster (shingles) involving the scalp follows a nerve distribution, usually one-sided, with pain that may precede the rash by days.10 Early antiviral treatment within 72 hours of rash onset reduces severity and the risk of post-herpetic neuralgia.10 Anyone with a painful, one-sided scalp rash should see a clinician promptly.
What is not an infection
Several common scalp conditions are routinely mistaken for infection. Seborrhoeic dermatitis produces flaking and itch that can mimic mild tinea, but the underlying mechanism is an inflammatory response to commensal Malassezia yeast, not infection.11 Psoriasis causes thicker, silvery scale on well-defined plaques. Contact dermatitis from a new product produces redness and itch without pustules or broken hairs.
The practical signal that something is infectious rather than inflammatory: localised pus, tender swelling, fever, lymph nodes, or a rash that follows a nerve line. Diffuse flaking and itch across the whole scalp, without these features, is almost never infection.12
Scalp Infections
What they look like, why most scalp complaints are not infections, and when to see a clinician.
Most scalp complaints are not infections. Itch, flaking, oiliness and tenderness usually trace back to seborrhoeic dermatitis, psoriasis, contact reactions or simple irritation — see Dandruff and Scalp Psoriasis, Plainly for those. True infection is less common, and most cases fall into three families: fungal, bacterial, and viral.
The reason this matters is that the three families look different, behave differently, and need different treatment. Confusing one for another wastes time and sometimes makes things worse.
Fungal: tinea capitis and kerion
Tinea capitis is a fungal infection of the scalp caused by dermatophytes — most often Trichophyton and Microsporum species.1 It is predominantly a disease of children. Classic features are patchy hair loss with scale, broken hairs at the surface (“black dots”), and sometimes lymph nodes at the back of the neck.1
A kerion is the inflammatory form: a boggy, tender, pus-studded plaque that can be mistaken for a bacterial abscess.2 The pus is part of the immune response to the fungus, not a separate bacterial problem, and incising it does not help.
The point worth keeping is this: topical antifungal shampoos alone do not cure tinea capitis. Oral antifungal treatment is required, typically griseofulvin or terbinafine, for several weeks.3 Shampoos help reduce shedding of spores to household contacts but they do not reach the hair shaft itself.3
Bacterial: folliculitis, furuncles and impetigo
Bacterial scalp infections most commonly involve Staphylococcus aureus.4 Superficial folliculitis presents as small, tender, pus-tipped bumps around individual hair follicles. A furuncle (boil) is a deeper, more painful nodule. Impetigo, more common in children, shows honey-coloured crusts.5 The same folliculitis pattern in the beard is covered in Beard & Skin Beneath.
Most superficial bacterial infections of the scalp respond to topical antibiotics and gentle cleansing.4 Deeper or recurrent infection, fever, or spreading redness warrants oral antibiotics and clinical assessment, particularly given the rise of methicillin-resistant strains.6
Two scalp-specific conditions deserve naming. Folliculitis decalvans is a chronic, scarring form of folliculitis that progressively destroys follicles and leaves smooth patches of permanent hair loss.7 Dissecting cellulitis of the scalp produces deep, interconnected nodules and sinus tracts, more common in young men, and is poorly responsive to simple antibiotics.8 Both are scarring, both need specialist care, and neither resolves with over-the-counter measures.
Viral: herpes simplex and herpes zoster
Viral infections of the scalp are uncommon but worth recognising. Herpes simplex can occur on the scalp, presenting as grouped vesicles on a red base, often painful or tingling before the rash appears.9
Herpes zoster (shingles) involving the scalp follows a nerve distribution, usually one-sided, with pain that may precede the rash by days.10 Early antiviral treatment within 72 hours of rash onset reduces severity and the risk of post-herpetic neuralgia.10 Anyone with a painful, one-sided scalp rash should see a clinician promptly.
What is not an infection
Several common scalp conditions are routinely mistaken for infection. Seborrhoeic dermatitis produces flaking and itch that can mimic mild tinea, but the underlying mechanism is an inflammatory response to commensal Malassezia yeast, not infection.11 Psoriasis causes thicker, silvery scale on well-defined plaques. Contact dermatitis from a new product produces redness and itch without pustules or broken hairs.
The practical signal that something is infectious rather than inflammatory: localised pus, tender swelling, fever, lymph nodes, or a rash that follows a nerve line. Diffuse flaking and itch across the whole scalp, without these features, is almost never infection.12
When to see a clinician
See a clinician for: patchy hair loss with scale in a child; a boggy or pus-filled scalp lump; honey-coloured crusts; a painful one-sided rash; fever with scalp tenderness; or any scalp problem that is worsening despite reasonable care. Scarring conditions, in particular, are time-sensitive. Treatment started early preserves follicles; treatment started late does not bring them back. For thinning related to hair loss rather than infection, see Thinning, Without the Panic.
Most scalp complaints are not infections, but the ones that are deserve to be named correctly and treated promptly. Guesswork at home is fine for flaking. It is not fine for pus, pain, or hair coming out in patches.
Sources
- Hay RJ. Tinea Capitis: Current Status. Mycopathologia. 2017;182(1-2):87–93.
- Proudfoot LE, Higgins EM, Morris-Jones R. A retrospective study of the management of pediatric kerion in Trichophyton tonsurans infection. Pediatr Dermatol. 2011;28(6):655–7.
- Gupta AK, Drummond-Main C. Meta-analysis of randomized, controlled trials comparing particular doses of griseofulvin and terbinafine for the treatment of tinea capitis. Pediatr Dermatol. 2013;30(1):1–6.
- Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the IDSA. Clin Infect Dis. 2014;59(2):e10–52.
- Hartman-Adams H, Banvard C, Juckett G. Impetigo: diagnosis and treatment. Am Fam Physician. 2014;90(4):229–35.
- Liu C, Bayer A, Cosgrove SE, et al. Clinical practice guidelines by the IDSA for the treatment of MRSA infections in adults and children. Clin Infect Dis. 2011;52(3):e18–55.
- Otberg N, Kang H, Alzolibani AA, Shapiro J. Folliculitis decalvans. Dermatol Ther. 2008;21(4):238–44.
- Scheinfeld N. Dissecting cellulitis (Perifolliculitis Capitis Abscedens et Suffodiens): a comprehensive review focusing on new treatments and findings. Dermatol Online J. 2014;20(5):22692.
- Fatahzadeh M, Schwartz RA. Human herpes simplex virus infections: epidemiology, pathogenesis, symptomatology, diagnosis, and management. J Am Acad Dermatol. 2007;57(5):737–63.
- Dworkin RH, Johnson RW, Breuer J, et al. Recommendations for the management of herpes zoster. Clin Infect Dis. 2007;44 Suppl 1:S1–26.
- Luelmo-Aguilar J, Santandreu MS. Folliculitis: recognition and management. Am J Clin Dermatol. 2004;5(5):301-310.
- Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections. Clin Infect Dis. 2014;59(2):e10-52.
- Hartman-Adams H, Banvard C, Juckett G. Impetigo: diagnosis and treatment. Am Fam Physician. 2014;90(4):229-235.
- Liu C, Bayer A, Cosgrove SE, et al. Clinical practice guidelines by the IDSA for the treatment of MRSA infections in adults and children. Clin Infect Dis. 2011;52(3):e18-55.
- Hay RJ. Tinea capitis: current status. Mycopathologia. 2017;182(1-2):87-93.
- Otberg N, Kang H, Alzolibani AA, Shapiro J. Folliculitis decalvans. Dermatol Ther. 2008;21(4):238-244.
- Gupta AK, et al. Treatment of tinea capitis. J Am Acad Dermatol. 1999;40(2 Pt 1):253-270.
- Scheinfeld N. Dissecting cellulitis (Perifolliculitis Capitis Abscedens et Suffodiens): a comprehensive review. Dermatol Online J. 2014;20(6).
- Fatahzadeh M, Schwartz RA. Human herpes simplex virus infections: epidemiology, pathogenesis, symptomatology, diagnosis, and management. J Am Acad Dermatol. 2007;57(5):737-763.
- Dworkin RH, Johnson RW, Breuer J, et al. Recommendations for the management of herpes zoster. Clin Infect Dis. 2007;44 Suppl 1:S1-26.
- Borda LJ, Wikramanayake TC. Seborrhoeic dermatitis and dandruff: a comprehensive review. J Clin Investig Dermatol. 2015;3(2).
- Schwartz RA, Janusz CA, Janniger CK. Seborrhoeic dermatitis: an overview. Am Fam Physician. 2006;74(1):125-130.
- Borda LJ, Wikramanayake TC. Seborrheic dermatitis and dandruff: a comprehensive review. J Clin Investig Dermatol. 2015;3(2):10.13188/2373-1044.1000019.
- Schwartz RA, Janusz CA, Janniger CK. Seborrheic dermatitis: an overview. Am Fam Physician. 2006;74(1):125–30.
Scalp Infections
Most scalp complaints are not infections. The ones that are — folliculitis, tinea capitis, cellulitis, herpes zoster — require specific treatment. How to tell the difference, and when to stop guessing.
Most of what people describe as scalp problems are not infections. Dandruff is not an infection. Seborrhoeic dermatitis is not an infection. Scalp psoriasis is not an infection. Scalp infections proper are a distinct category — fewer in number, more urgent in nature, and treatable with targeted therapy when identified correctly. The difficulty is that several infections look, at first glance, like the benign non-infectious conditions that precede them in most people's diagnostic journeys.
Folliculitis: the most common true scalp infection.
Folliculitis is an infection of the hair follicle, typically bacterial, most often caused by Staphylococcus aureus.1 It presents as small red or white-headed papules or pustules at the follicle opening — essentially pimples on the scalp. They may be tender or itchy. They occur in clusters and tend to recur in the same areas.
Mild folliculitis often resolves with improved hygiene — regular washing with an antibacterial shampoo, avoiding occlusive products that trap sweat and sebum, and not wearing tight headgear that generates friction. More persistent or widespread folliculitis may require a topical antibiotic (mupirocin, clindamycin) or, for deeper infections, oral antibiotics.2 Recurrent folliculitis that does not respond to standard treatment should prompt consideration of MRSA, for which topical mupirocin nasal decolonization and skin antiseptics may be needed.3
A variant worth knowing: Malassezia folliculitis (sometimes called pityrosporum folliculitis) presents similarly but is fungal rather than bacterial. It tends to occur on the scalp and upper back, often worsens with antibiotic use, and responds to antifungal treatment rather than antibiotics.4 The two can look identical. If folliculitis does not respond to antibiotics within two weeks, a fungal cause should be considered.
Tinea capitis: the infection that looks like dandruff.
Tinea capitis is a dermatophyte infection of the scalp — a fungal infection, but not Malassezia. It is caused by species of Trichophyton or Microsporum that infect the hair shaft itself. In adults it is uncommon; in children it is the most common scalp infection globally.5
It can present in several ways: patchy hair loss with scale and broken hairs at the scalp surface (the most recognizable presentation); diffuse flaking that looks like dandruff but does not respond to antifungal shampoos; or, in the inflammatory variant called a kerion, a boggy, pus-filled lump that is painful and tender and can leave scarring alopecia if not treated promptly.6
The critical point: tinea capitis does not respond to topical antifungals. The organisms infect the hair shaft, which topical agents cannot penetrate adequately. Oral antifungal therapy — terbinafine or griseofulvin — is required, typically for four to eight weeks.7 If a child in the household has patchy hair loss with scale, tinea capitis should be near the top of the differential diagnosis and a clinician consulted.
Cellulitis and abscess: the serious end.
Scalp cellulitis is a bacterial infection of the deeper layers of the skin — below the follicle, into the dermis and subcutaneous tissue. It presents as a painful, warm, swollen area of scalp, usually without a central pustule. There may be fever. The borders of the involved area are not sharply defined. This is a condition requiring prompt medical attention and typically oral antibiotics; more severe cases require intravenous treatment.8
A scalp abscess — a localized collection of pus — presents as a fluctuant, tender lump. It usually requires incision and drainage in addition to antibiotics. Home treatment is not appropriate for either of these.
If a scalp complaint has not responded to two reasonable attempts at self-treatment, a practitioner conversation is more efficient than a third guess. Members have direct access to that conversation.
Explore MembershipHerpes zoster: the painful one-sided rash.
Herpes zoster (shingles) can affect the scalp when the virus reactivates in the trigeminal nerve. It presents as a painful, one-sided rash following a dermatomal distribution — typically beginning with pain and tingling before the vesicular rash appears. The rash does not cross the midline. It may involve the scalp, forehead, and eye region on the same side.9
Early treatment with oral antivirals (aciclovir, valaciclovir, famciclovir) is most effective when started within 72 hours of rash onset. If the eye appears to be involved, urgent ophthalmological assessment is needed. This is not a condition to wait out or treat topically.10
What infection looks like versus what it doesn't.
Features suggesting infection rather than a non-infectious scalp condition: pain or tenderness (not just itch); warmth to touch; pustules with a central whitehead at the follicle; a boggy or fluctuant lump; patchy hair loss in a child with scale; a painful one-sided rash; fever with any scalp complaint.
Features more consistent with dandruff, psoriasis, or non-infectious scalp conditions: diffuse flaking without pain; bilateral and symmetric involvement; itch without tenderness; a pattern that has been present for months or years and waxes and wanes with seasons or stress.
When to see a clinician.
See a clinician for: patchy hair loss with scale in a child; a boggy or pus-filled scalp lump; honey-coloured crusts on the scalp (impetigo); a painful one-sided rash; fever with any scalp complaint; cellulitis that is spreading rather than resolving.
Most scalp complaints are not infections, but the ones that are deserve to be named correctly and treated promptly. Guesswork at home is fine for flaking. It is not adequate for folliculitis that keeps recurring, for a kerion that is damaging follicles, or for zoster that may be threatening vision.
Sources
Owls & Wolves — Pasadena, CA
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