Bacterial Folliculitis

Clinical Snapshot

Bacterial folliculitis is infection and inflammation centred on hair follicles, producing papules and pustules. Staphylococcus aureus is the dominant cause; Pseudomonas aeruginosa produces a distinct hot-tub-associated pattern.^[1] Few superficial pustules need only trigger removal and local care; extensive, recurrent, or refractory disease needs culture and systemic therapy. A furuncle (boil) is a deeper S. aureus infection extending suppuration into the dermis and subcutaneous tissue; interconnecting furuncles that coalesce form a carbuncle — both belong in the purulent skin-infection pathway, not this one.

Recognize the Condition

Multiple small erythematous papules and pustules centred on individual hair follicles

Bacterial folliculitis — small papules and pustules, each centred on a hair follicle. (Da pacem Domine, CC0, Wikimedia Commons)

Typical findings

Small erythematous papules or pustules centred on individual follicles.
May itch, burn, or be mildly tender.
Shaving areas, buttocks, thighs, trunk, and occluded/intertriginous areas are common sites.
Hot-tub folliculitis appears after contaminated-water exposure and may involve areas covered by swimwear, typically 8 hours to 5 days after exposure.

Do not misclassify: a deep, painful, fluctuant nodule is no longer simple folliculitis — manage it as a furuncle/abscess instead.

Risk Factors

Friction, sweating, occlusion, and tight clothing.
Shaving, waxing, or other hair removal causing follicular trauma.
Hot-tub or pool exposure for the Pseudomonas pattern.
Staphylococcus aureus carriage or prior recurrent staphylococcal infection.
Diabetes, immunosuppression, or other conditions that impair host defence.

Red Flags & Refer

Refer promptly for any of the following:

Rapidly progressive infection.
Extensive surrounding cellulitis.
Systemic illness (fever, malaise).
Severe immunocompromise.
Facial or periorbital involvement.
Deep fluctuant lesions suggesting abscess.
Recurrent unexplained disease.
A pattern suggesting hidradenitis suppurativa (recurrent painful nodules and scarring in the axillae or groin).

Assessment & Diagnosis

Diagnosis is usually clinical. Ask about shaving, friction, occlusion, hot-tub exposure, prior MRSA, recurrent lesions, diabetes, and immunosuppression.

When to cultureSwab a pustule for culture and sensitivity when disease is extensive, recurrent, resistant to treatment, associated with MRSA risk factors, or when gram-negative/Pseudomonas infection is suspected.^[1]

Important mimics

Pseudofolliculitis from shaving/ingrown hairs (noninfectious, induced by friction and occlusion).
Acneiform eruptions.
Malassezia (fungal) folliculitis.
Hidradenitis suppurativa when recurrent painful nodules/scarring affect the axillae or groin.

Treatment Targets

Stop formation of new pustules.
Resolve follicular inflammation and discomfort.
Prevent progression to furuncle, abscess, or cellulitis.
Correct the mechanical or environmental trigger to prevent recurrence.

Choose Initial Treatment

Direct treatment rule

Mild, localized disease (few pustules)

Remove the trigger and use supportive care only. Warm compresses and drying measures; no antibiotic is needed. Most mild folliculitis resolves spontaneously.

Persistent localized disease after supportive care

1st line: a short defined course of topical mupirocin or fusidic acid.

Extensive or refractory staphylococcal disease

1st line: culture the pustule, then oral cephalexin.

Alternative when MRSA is suspected/confirmed: doxycycline or trimethoprim-sulfamethoxazole.

Hot-tub (Pseudomonas) folliculitis

Supportive care only in mild, otherwise-well patients — it is usually self-limited.

Reserve ciprofloxacin for severe, extensive, or markedly immunocompromised patients, and only when culture or strong clinical context supports Pseudomonas.^[1]

Non-Pharmacologic Treatment

Stop close shaving until inflammation resolves.
Reduce friction, heat, occlusion, and moisture; loosen tight clothing.
Use warm compresses and gentle cleansing.
Do not share razors or towels.
Launder contaminated clothing and bedding; use careful hand hygiene.

Pharmacologic Treatment Options

Drug / intervention	Role	Dose / use	Important adverse effects	Teaching points
Mupirocin 2% topical Preferred	Persistent localized staphylococcal folliculitis after supportive care	Apply BID-TID for 5-7 days	Local stinging, rare allergic contact dermatitis	Do not use beyond a short defined course; resistance increases with repeated exposure.
Fusidic acid 2% topical Preferred	Alternative topical anti-staphylococcal treatment	Apply BID-TID for 5-7 days	Rare allergic contact dermatitis	Do not use chronically for wound colonization.
Cephalexin Preferred	Extensive/refractory disease, MRSA not suspected	250-500 mg PO QID	GI upset, hypersensitivity	1st-line oral agent. Probenecid increases levels.
Doxycycline Alternative	MRSA suspected/confirmed, or extensive Pseudomonas-risk disease	100 mg PO BID	Photosensitivity, esophagitis	Avoid in pregnancy and in children under 8 years.
Sulfamethoxazole/Trimethoprim Alternative	Suspected/documented MRSA	1-2 DS tablets PO BID	Rash, hyperkalemia, cytopenias	Not reliable streptococcal coverage — add separate coverage if cellulitis is also present.
Ciprofloxacin Special situation	Severe/extensive hot-tub folliculitis, high-risk or immunocompromised patient only	500-750 mg PO BID	Tendinopathy, neuropathy, CNS/QT effects	Most hot-tub folliculitis is self-limited — do not use routinely; Health Canada has issued a safety warning restricting fluoroquinolone use.<cite data-reference-id="bf6a91c3-40d8-43e2-8888-5ca7a109f3dc"></cite>

Special Populations

Pregnancy

Use local care first. If systemic therapy is needed, cephalexin is preferred when the organism is susceptible. Avoid routine doxycycline and trimethoprim-sulfamethoxazole when a safer effective option exists.

Immunocompromised patients

Use a lower threshold for culture, systemic therapy, and referral because disease may progress rapidly or involve unusual organisms.

Recurrent staphylococcal folliculitis

For selected patients with confirmed recurrent S. aureus disease, a decolonization course (intranasal mupirocin twice daily for 5 days plus daily chlorhexidine body wash for 5 days) may be considered.^[2]

Monitoring & Follow-Up

Localized disease should stop producing new lesions within several days. Reassess at approximately 48-72 hours after starting systemic therapy, or sooner if spreading occurs. Lack of response requires culture review, reconsideration of the diagnosis, and evaluation for evolving abscess.

Treatment Failure / Next Step

Confirm folliculitis rather than pseudofolliculitis or fungal (Malassezia) disease.
Confirm friction/occlusion/shaving triggers were actually removed.
Obtain bacterial culture if not already done.
Switch to susceptibility-directed therapy.
For recurrent S. aureus disease, assess carriage and consider a decolonization protocol.

Common Errors to Avoid

Giving oral antibiotics for a few uncomplicated pustules.
Using topical antibiotics repeatedly for weeks.
Treating hot-tub folliculitis automatically with ciprofloxacin.
Missing a developing furuncle/abscess that requires drainage.
Calling shaving-related pseudofolliculitis a bacterial infection.

Clinical Decision Algorithm

Algorithm A — Localized versus extensive bacterial folliculitis

Follicular papules/pustules centred on hair follicles

Remove friction, occlusion, shaving irritation, and moisture; use warm compresses and drying measures

Localized / few lesions

Observe and use supportive care first

If not improving after about 7 days, give a short course of topical mupirocin or fusidic acid

Extensive / recurrent / refractory

Swab pustule for culture and sensitivity

Start oral cephalexin; add MRSA-active therapy (doxycycline or TMP-SMX) only when risk factors or culture support it

Algorithm B — Hot-tub / Pseudomonas pattern

Folliculitis after hot-tub, pool, or contaminated-water exposure

Mild / otherwise well

Supportive care only — spontaneous resolution is expected

Extensive, very symptomatic, or markedly immunocompromised

Culture when feasible; consider ciprofloxacin only if Pseudomonas is supported and benefit outweighs fluoroquinolone risk

Drug Tables

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

Topical anti-staphylococcal agents

Used for localized disease after supportive measures fail.

Drug	Dosage	Adverse effects	Comments
Mupirocin 2%	Treatment (all ages): Apply BID-TID for 5-7 days Decolonization (recurrent disease): Intranasal BID for 5 days, combined with daily chlorhexidine body wash for 5 days^[2]	Local stinging, rare contact dermatitis	Covers MSSA and MRSA. Resistance increases with repeated exposure.
Fusidic acid 2%	Treatment (all ages): Apply BID-TID for 5-7 days	Rare allergic contact dermatitis	Covers MSSA and MRSA. Use only for a defined course.

Oral beta-lactams

First-line for extensive/refractory disease when MRSA is not a concern.

Drug	Dosage	Adverse effects	Comments
Cephalexin	Adults: 250-500 mg PO QID Adults, severe disease: Up to 1000 mg PO QID Children: 25-50 mg/kg/day divided Q6H PO (max 1000 mg/day)	GI upset, hypersensitivity	First-line oral agent. Probenecid increases serum levels.
Cefadroxil	Adults: 500 mg PO daily-BID Adolescents: 250 mg PO BID, or adult dose Children: 20 mg/kg PO once daily (max 500 mg/day)	GI upset, hypersensitivity	Convenient once/twice-daily alternative to cephalexin.
Cloxacillin	Adults: 250-500 mg PO QID Children: 12.5-25 mg/kg PO QID (max 500 mg/dose)	GI upset, hypersensitivity, hepatic enzyme elevation	Limited by poor oral bioavailability, narrow spectrum, and QID dosing.

MRSA-active oral agents

Reserve for confirmed/suspected MRSA or high local MRSA prevalence.

Drug	Dosage	Adverse effects	Comments
Doxycycline	Adults: 100 mg PO BID Children over 8 years: 2-4 mg/kg/day divided Q8-12H PO (max 100 mg/dose)	Photosensitivity, esophagitis	Avoid in pregnancy and children under 8. Absorption reduced by iron/calcium/antacids.
Sulfamethoxazole/Trimethoprim	Adults: 1-2 DS tablets PO BID Infants (2 months+), children, adolescents: 8-12 mg/kg/day (TMP component) divided Q12H PO	Rash, hyperkalemia, cytopenias	Not reliable streptococcal coverage; interacts with warfarin, phenytoin, methotrexate.
Clindamycin	Adults: 300-450 mg PO TID Children over 1 month: 25-40 mg/kg/day divided Q8H PO (max 450 mg/dose)	Diarrhea, C. difficile infection	Culture-directed use when local susceptibility supports it.

Selected Pseudomonas coverage

Only for severe/extensive hot-tub folliculitis in a high-risk host.

Drug	Dosage	Adverse effects	Comments
Ciprofloxacin	Adults: 500-750 mg PO BID	Tendinopathy, peripheral neuropathy, CNS effects, QT prolongation	Health Canada safety warning restricts routine fluoroquinolone use — reserve for specific indications; generally avoided in children.<cite data-reference-id="bf6a91c3-40d8-43e2-8888-5ca7a109f3dc"></cite>

References

Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America — Clinical Infectious Diseases (Stevens DL, Bisno AL, Chambers HF, et al.). Clin Infect Dis 2014;59(2):e10-e52
Staphylococcus aureus decolonization for recurrent skin and soft tissue infections in children — Canadian Family Physician (Smith CH, Goldman RD). Can Fam Physician 2012;58(12):1350-1352
Fluoroquinolones – Risk of disabling and potentially permanent serious side effects — Health Canada. Health Canada Recalls and Safety Alerts, January 2017
Skin diversity erythema description guidance — British Association of Dermatologists (Gass M, Dadzie OE, Dlova N, et al.). February 2021

Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.