What type of injections, such as Botox (botulinum toxin), are used to treat excessive sweating (hyperhidrosis)?

Botulinum Toxin Injections for Hyperhidrosis

Botulinum toxin (Botox) injections are the primary injectable treatment for excessive sweating (hyperhidrosis), particularly for axillary (underarm) hyperhidrosis that has failed topical treatments. 1, 2

Mechanism and Efficacy

Botulinum toxin type A works by blocking acetylcholine release at cholinergic nerve terminals that innervate sweat glands, effectively preventing sweat production in the treated areas 3, 4. This mechanism is distinct from its neuromuscular blocking effects used in other conditions.

For axillary hyperhidrosis specifically:

• Complete abolition of sweating occurs within 3-7 days of injection 4
• Objective sweat reduction of 28-37% persists for at least 13 weeks 5
• Subjective improvement of 56-67% is maintained through 13 weeks 5
• Duration of effect typically ranges from 6-9 months, though some studies report 3-9 weeks for axillary sites 3, 2

Treatment Algorithm by Body Site

Axillary (Underarm) Hyperhidrosis

• First-line: Topical aluminum chloride 1
• Second-line: Botulinum toxin injections 1
• Third-line: Oral medications (glycopyrrolate or clonidine) 1
• Fourth-line: Local surgery 1
• Fifth-line: Endoscopic thoracic sympathectomy 1

Palmar (Hand) and Plantar (Foot) Hyperhidrosis

• First-line: Topical treatments 1
• Second-line: Oral medications (glycopyrrolate 1-2 mg once or twice daily preferred over clonidine 0.1 mg twice daily) 1
• Third-line: Iontophoresis 1
• Fourth-line: Botulinum toxin injections 1
• Fifth-line: Endoscopic thoracic sympathectomy (palmar only; not recommended for plantar) 1

Craniofacial Hyperhidrosis

• First-line: Oral medications (glycopyrrolate or clonidine) 1
• Botulinum toxin may be useful in select cases 1

Dosing Specifications

Axillary hyperhidrosis:

• Total doses range from 200-400 mouse units (Dysport) or 80-130 mouse units (Botox) 3
• Typical protocol: 200 mouse units Dysport distributed across 6 injection sites per axilla 5
• Alternative: 3 mouse units Botox per 4 cm² skin area 4

Palmar hyperhidrosis:

• Similar dosing to axillary sites, but requires careful technique 3
• Duration of anhidrotic effect is longer: 20-50 weeks 3

Critical Safety Considerations

Pain management is essential for palmar injections:

• Local anesthetics or nerve blocks (ulnar and median nerves) are necessary due to significant injection pain 3

Palmar injection complications:

• Transient weakness of small hand muscles occurs due to the narrow therapeutic window 3
• This limits the utility of botulinum toxin for palmar hyperhidrosis compared to axillary sites 3

General safety profile:

• No serious side effects observed in controlled trials 5, 4
• Injections are generally well tolerated for axillary sites 3
• High patient satisfaction rates 2

Common Pitfalls to Avoid

Inadequate patient counseling about treatment duration: Patients must understand this is not a permanent solution and requires repeat injections every 6-9 months (or 3-9 weeks in some cases) 3, 2. This represents a significant ongoing time and financial commitment.

Treating palmar hyperhidrosis without proper anesthesia: The pain from palmar injections is substantial and will result in poor patient tolerance and incomplete treatment 3.

Using botulinum toxin as first-line therapy: Topical treatments should always be attempted first, as they are less invasive and less expensive 1. Botulinum toxin is reserved for cases resistant to conventional treatment 3, 5.

Ignoring the therapeutic window in palmar injections: The risk of hand muscle weakness means dosing must be carefully calibrated, making palmar treatment more technically challenging than axillary treatment 3.