What term is used for effects of a drug that are undesirable but not necessarily harmful?

The term 'side effects' refers to the unintended and often undesirable effects that occur in addition to the desired therapeutic effects of a drug. While these effects are not necessarily harmful, they can be bothersome or inconvenient. Side effects are a common occurrence with many medications and can range from relatively mild symptoms, such as gastrointestinal discomfort, to more significant reactions that can affect a patient's quality of life.

In contrast, toxic reactions typically imply more serious or harmful effects that arise from overdoses or heightened sensitivity to a drug. Allergic reactions involve the immune system and result in hypersensitivity responses, which can be serious and potentially life-threatening. Adverse reactions encompass a broader range of negative effects, including harmful and severe reactions, not just those that might be considered mild or not directly harmful. Therefore, 'side effects’ is the most appropriate term to describe these undesired effects that do not necessarily result in harm.