Making homemade kombucha can be safe, but it is important to follow hygiene rules and use quality ingredients. It is also important to avoid contamination with harmful bacteria and to control the fermentation process to prevent excessive growth of acetic acid or other potentially harmful substances. To reduce the risk of contamination, it is recommended to sterilize the equipment and use fresh tea and granulated white sugar. It is also recommended to avoid drinking kombucha that has been fermented for too long or that has an unusual taste or smell. In general, people with a weakened immune system or health problems should consult a doctor before starting to consume kombucha or any other home-fermented product.