Some claim that smells can have an impact on mood, and others go farther to say that smells can even improve health. Certainly some aromatherapeutic materials have been shown to have antibacterial and antifungal properties. As the field advances, more systematic analysis will reveal the best opportunities for its use. The inability to smell is a condition called anosmia. Anosmic people have lost the ability to smell or were born without it.
People can lose their ability to smell from head injuries or the aging process.
Anosmia can make life less stimulating and can lead to depression. Research on mice has shown that anosmic mice tend not to mate. Losing your ability to smell can signal the onset of worse diseases, including diabetes, hypertension, malnutrition, and some degenerative diseases of the nervous system such as Parkinson's disease or Alzheimer's disease. Researchers in Syracuse are even looking at loss of smell as a predictor of developing AIDS in HIV positive patients. The sense of smell fades for most people as they age, and it's not yet clear why.