Food supplements and tea containing St. John's wort can have harmful effects on health. This has been shown in a study by RIVM. RIVM therefore advises consumers to be cautious with the use of herbal preparations containing St John's wort and not use these products in combination with medicines. 

People use herbal preparations (food supplements and herbal tea) with St John's wort, amongst others, to sleep better. It is not known how many people use herbal preparations with St. John's wort.  

St John's wort in combination with medicines

St John's wort can reduce the effect of medicines. Herbal preparations with St John's worth reduce, for example, the effect of certain medicines prescribed for fungal or viral infections and cancer (chemotherapy). St John's can enhance the effect of, for instance, antidepressants or sedatives. RIVM therefore advises consumers not to combine herbal preparations with medicines.

Risks of using St John's wort without medicines

Even without the interaction with medicines, the use of herbal preparations with St John's wort may pose health risks. For example, sunburn can occur if people sit in the sun after using St. John's wort. Other complaints may occur such as dizziness, diarrhoea and anxiety. It is not known what the long-term effects are of St John’s wort. There is also insufficient information available to determine whether the use of St John's wort during pregnancy is safe for the unborn child. Moreover, the composition of herbal preparations containing St John's wort is often unknown. This makes it difficult to estimate the effects of a product.