One side effect of COVID-19 includes the loss of smell and taste. For some, this can last for months.

One of the most striking symptoms of COVID-19 is the temporary loss of smell and taste. For a subset of people, these symptoms can last for months, creating great stress and anxiety.But something called “smell therapy” is helping them cope.

Also known as olfactory retraining or smell training, research suggests it’s an affordable, non-invasive and convenient way to treat the loss of smell.

Smell therapy is simple: It consists of exposing the person to strong scents, like eucalyptus, rose, lemon and cloves, for a period of 15 to 20 seconds, twice a day. These smells are supposed to evoke the four primary smells: floral, fruity, aromatic and resinous.

In a study published in the journal Laryngoscope, researchers found that after a period of 12 weeks, participants reported better recognition of smells when compared to those who didn’t follow the smell tests.

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“It’s important that you understand that, for example, this is a rose smell you’re supposed to be smelling,” otolaryngologist Dr. Raj Sindwani told Self. “The idea is for you to try and think about what roses smell like and what they look like by combining visual imagery with the stimulation of the isolated scent.”

Despite the research, the way in which the olfactory system works is not wholly understood. In a system that’s functioning normally, the odor particles in the air signal the receptors in the sinuses, which then send a signal to the area of smell in the brain. Viral illnesses can harm these receptors.

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Smell therapy is supposed to engage the brain in the act of smelling, engaging neuroplasticity, helping it to grow, reorganize itself and create new pathways and links related to smell.

While the majority of people who suffer from COVID-19 and lose their sense of smell regain it in a couple of weeks, this isn’t the case for everyone. For some, their smell comes back slowly and may never fully recover. Smell therapy might help speed the recovery process along, providing these people with a sense of control.