Harper, aged 16, is generally well but suffers recurrent upper respiratory tract infections and takes lots of time off school.

She appears well, her menses are normal, she does not smoke cigarettes and there is no history of an eating disorder. Harper is finding Year 11 studies stressful.

Physical examination reveals a healthy child of normal height and weight. She has no pallor or signs to indicate iron or nutritional deficiency.

What advice can we provide Harper with to help support her immune system?