Objective Hajj is an important component of Islam. This study aimed to determine the effect of wearing a cotton towel or plain cotton ihram on the onset of respiratory symptoms and fractional exhaled nitric oxide (FeNO) levels in Hajj pilgrims. Methods One hundred male nonsmoking subjects (age: 20–60 years) without a previous clinical history of respiratory illnesses were included. Fifty subjects were dressed in a cotton towel ihram and 50 wore a plain cotton ihram (control group). Respiratory symptoms and FeNO levels were recorded on the day before leaving for Hajj, when ihrams were removed, and when the pilgrims had returned home. Results Pilgrims who wore cotton towel ihrams showed significantly higher rates of respiratory symptoms, including being generally ill, coughing, a sore throat, and a runny nose, than those who wore plain ihrams. FeNO levels also tended to be higher in pilgrims who wore a cotton towel ihram compared with those with a plain cotton ihram during and after Hajj. Conclusions Hajj pilgrims who wear cotton towel ihrams may have a risk of respiratory symptoms, including a cough, sore throat, and runny nose. Therefore, a plain cotton ihram is advisable while performing Hajj to minimize respiratory illness.