PSK has been shown to have minimal or no adverse effects although early studies have reported occasional effects including coughing, nail pigmentation, constipation and diarrhoea48,49.
The side effects were significantly reduced when PSK was formulated in tablets or capsules instead of the medication taken in the powder form reconstituted in water48.
Low grade gastrointestinal and haematological toxicities have been reported, which may be due to chemotherapeutic agents and radiation themselves51,52.
According to Drug Adverse Reaction Report of the Japanese Ministry of Health and Welfare, side effects caused by PSK were experienced in 114 of a total of 11,300 cancer patients (1.01%)65.
The main complaints were associated with diarrhoea and nausea.