Primary focal hyperhidrosis interferes with daily activities. Limited efficacy, costs, side effects and complications are issues of concern for most current therapeutic modalities. In this study the invetigators aim to evaluate the efficacy of topical oxybutynin 10% gel in treating primary focal hyperhidrosis. 60 patients with primary focal hyperhidrosis will be recruited. Topical oxybutynin 10% gel will be assigned to the right or left axilla, palm or sole and a placebo compound to the contralateral side for a total of 30 days. The Hyperhidrosis Disease Severity Scale (HDSS) and Dermatology Life Quality Index (DLQI) questionnaires will be administered before and after treatment, and 2 noninvolved blinded physicians will score the results using starch-iodine tests. The participants will grade the sweat reduction on both sides and rated their satisfaction.

This study will be performed at the Tel Aviv Medical Center. Written informed consent will be obtained from all 60 participants prior to entering the study. patients with primary focal hyperhidrosis (palmar hyperhidrosis, axillary hyperhidrosis, plantar hyperhidrosis) who receive no topical or oral anticholinergics, iontophoresis treatment or botulinum toxin injections during the 6 months prior to study entry and did not undergone sympathectomy will be recruited. Demographic data, including gender, age and medical history will be collected before enrollment in the study, and the following patients will be excluded: pregnant or lactating women, individuals with conditions that may cause secondary hyperhidrosis, individuals with a history of eczema, seborrhea, psoriasis, glaucoma, micturition disorder, gastric retention, myasthenia gravis, angioedema, Sjögren's syndrome, or Sicca syndrome, and candidates older than 60 years or younger than 18 years.

The study will follow a prospective, randomized, double blind, placebo-controlled design. Each participant will be given a pair of test jars (designated as "'gel A"' and "'gel B"'). The investigators will use a designated software to randomize the jars (either A or B) which contained 10% oxybutynin gel or a placebo aqueous gel. The two jars are identical in shape, size and weight, as well as color, odor and consistency. The patients will be instructed to apply 1 cm of gel A or B on clean, dry and intact skin of one sweating area (right or left palms, soles or axillae) twice daily for 30 days. In addition, the participants will be instructed to avoid contact of the gel with the eyes, nose, mouth, and not to wash the areas for 4 hours post-application. The participants will be also instructed not to use any concomitant topical or systemic medication during the entire treatment period. Each jar will be weighed by a digital scale before treatment initiation and on the 30th day of treatment.

The participants will interviewed twice, first at the time of screening before the initial application and then following the completion of the 30th day of treatment. The participants will be asked to rate the severity of their condition using the hyperhidrosis disease severity scale in which a score of 3 or 4 indicates severe hyperhidrosis while a score of 1 or 2 indicates mild or moderate hyperhidrosis. The therapeutic results will be considered as "excellent" or "good" if the patient indicate a reduction of 2 or 1 points, respectively, on the HDSS score.

In addition, quality of life will be assessed by a modified Dermatology Life Quality Index. The maximum score is 30, with 0 indicating a negligible effect of the disorder on the patient's quality of life and 30 indicating a significant impact. A change of 0-1 point on the mDLQI score will be interpreted as reflecting no effect on the patient's life, a change of 2-5 points as a small effect, 6-10 points as a moderate effect, 11-20 points as a very significant modification, and 21-30 points as the most significant impact possible.

At the end of the treatment, patients will complete a questionnaire evaluating the following:

1. Sweat reduction in the treated and in the control sweating areas (0 = no change, 1 = poor (limited improvement with the patient being very much aware of sweating), 2 = fair (marked improvement, with noticeable sweating under stressful conditions only, 3 = good (marked improvement with minimal sweating under stressful conditions), and 4 = excellent improvement, with cessation of sweating)
2. Global patient satisfaction (0 = dissatisfied, 1 = partially satisfied, 2 = satisfied, and 3 = highly satisfied).
3. Side effects: dry mouth, headache, dizziness, urine retention, constipation and application site reactions (pruritus or dermatitis).

All patients will undergo the Minor iodine-starch test. The tested area will be photographed under standard conditions using the Galaxy Camera (3G) EK-GC100 photography system. Photographs taken before and after 30 days of treatment will be independently assessed by two dermatologists who are unaware of the study design. All pairs of photographs will be graded as 0 = no change, 1 = minor change of <25%, 2 = moderate change between 25-50%, 3 = major change between 50-75%, and 4 = absence or near absence of sweating.

Both the study and control gels will be compounded in an Israeli compounding pharmacy.

Continuous variables will be fed into a tabular format as means ± standard errors and compared using the Wilcoxon paired test. Categorical variables will be tested using the Fisher exact test. Correlation between raters will evaluated using Spearman's correlation. All analyses were carried out using SPSS 23.0.2.

Inclusion Criteria:

• healthy individuals
• primary hyperhidrosis (axillary, palmar, plantar) diagnosed according to the recommended criteria4 : focal, visible and excessive sweating of at least 6 months duration without apparent cause, with at least two of the following characteristics: bilateral and symmetric, impairing daily activity, more than one episode per week, onset before age of 25 years, positive family history, cessation during sleep.
• given written informed patient consent of participation in the study

Exclusion Criteria:

• known history of conditions that may cause secondary hyperhidrosis
• eczema, seborrhea, psoriasis
• any other active lesion on treatment site
• any treatment for hyperhidrosis within 4 weeks
• Any medical condition that can be aggravated by anticholinergic medications: glaucoma, micturition disorders, gastric retention, myasthenia gravis, angioedema , known history of Sjögren's syndrome or Sicca syndrome
• iodine allergy
• lactation