The present study is a 12-week, randomized, double-blind, parallel control trial carried out in the Skin and Stem Cell Research Center affiliated to Tehran University of Medical Sciences between November 2019 and May 2020. The trial was registered at the Iranian registry of clinical trials on November 9th, 2019 (https://www.irct.ir/trial/43434 ; registration number: IRCT20191104045326N1). A written consent form was taken from eligible patients before recruitment in the trial.
We recruited patients with mild to moderate psoriasis, aged over 18 years old. Participants with the following conditions were included: a Psoriasis Area and Severity Index (PASI) of less than 30%, and a body surface area (BSA) of less than 10%, clinically diagnosed Plaque psoriasis, controlled psoriasis during last two months, not using Psoralen and phototherapy during 4 weeks ago, not participating in other studies during the previous month and at the same time. Patients were excluded if they (1) had different types of psoriasis such as psoriatic arthritis, pustular psoriasis, erythrodermic psoriasis, etc. (2) used corticosteroids and immunosuppressive drugs and systemic therapies during the last four weeks, (3) using some medications that may intensify psoriasis including beta-blockers, Calcium channel blockers, non-steroidal anti-inflammatory drugs, lithium, etc. (4) patients with cardiovascular and cancer diseases, (5) allergy to any components of syrup, (6) pregnancy and lactation, (7) Acute progressive psoriasis and erythroderma tendency.
Sample size estimation
Based on previous studies and considering the following formula as the sample size equation for comparing two populations, p1=15%, p0=40%, α=0.05, β=20%, the sample size was estimated at 45 individuals. Finally, considering a 10% loss to follow-up, 50 individuals were recruited in each group.
Randomization and intervention
Participants were randomly assigned to the intervention or control group using the random number sequence function in Excel and a 1:1 allocation ratio. Patients in the intervention group consumed two tablespoons (each tablespoon = 10 ml) of Melissa officinalis syrup three times per day (two tablespoons before each meal of breakfast/ lunch/ dinner) and patients in the control group received the same amount of placebo for 12 weeks.
Melissa officinalis syrup contained 3 grams of Lemon balm, 8 grams of Damask rose, and 1 gram of Fennel. Firstly, the decoction of these herbs was prepared. The herbs and 450 ml water were added to a pot and heated to boil gently. It boiled until the volume is reduced to 250ml. While boiling, some honey was added to sweeten it. The placebo syrup contained sugar, caramel coloring additive, and 1% rose water. The pharmacy department of traditional medicine college prepared both Melissa officinalis syrup and placebo. There is no detectable difference between Melissa officinalis syrup and placebo syrup in color, odor, viscosity, and containers. Patients were followed by a practitioner and they were able to ask their questions anywhere and anytime by telephone or face-to-face in the clinic.
The tools used for data collection were a socio-demographic questionnaire, Psoriasis Area and Severity Index (PASI), Life Quality Index (DLQI) questionnaire, and Visual Analogue Scale (VAS). PASI combines the severity of lesions and the body surface area involvement into one score. It has a range score from 0 (no disease) to 72 (maximum severity of the disease) . DLQI questionnaire is designed for adult patients with skin diseases and is a 4-point Likert scale questionnaire that each question gets a score from zero (not at all) to three (very much). The total DLQI score range from 0 to 30, that higher scores represent higher impairment of quality of life . A VAS scale measured the pruritus intensity. Patients draw a line on 0 to 10 cm VAS scale to determine their itching level at the beginning and end of the study. It is a reliable and valid instrument that is most widely used in epidemiologic and clinical trials. It has a range score from 0 to 10, of which 0 expresses no pruritus and 10 depicts intense pruritus .
We used SPSS version 19 (SPSS Inc., Chicago, IL, USA) for windows to perform data analysis. P values under 0.05 were regarded as significant. Categorical data were expressed in percentage (%), while continuous data were expressed in mean ± SD in evaluating patients' demographic details. Chi-square or Fisher exact test was used for the categorical data and Independent Samples t-Test was used for continuous data to show the differences. For comparison of PASI, DLQI, and VAS parameters between intervention and placebo groups, an independent t-test was applied at the first and end of the study. A paired sample t-test was also used to compare the mean of variables at pre and post-treatment in each group.