Our sense of smell is extremely important in everyday life. It can impact our memories and emotions. Our brain’s ability to process the smells in our environment through receptors in our nose is called olfactory processing. There are individual differences in sensory processing; some children can be hypersensitive to smells and be bothered by subtle smells in the environment. On the contrary, some children can be hyposensitive to smells and not seem to notice smells in the environment that other people easily sense, such as strong brewing coffee or a skunk. 

There are the four patterns of sensory processing: low registration, sensation seeking, sensory sensitive and sensation avoiding. 

Low registration: A child with low registration does not recognize or process all of the incoming sensory information, and they do not compensate by trying to gain more sensory input to meet their needs. They may seem uninterested, and inattentive to their surroundings.  

Sensation seeking: A child classified as sensation seeking does not recognize or process all of the incoming sensory information, but contrary to low registration, they actively try to gain this sensory input to meet their needs. They may be hyperactive, touch others often or engage in unsafe activities like jumping from heights. 

Sensory sensitive: A child classified as sensory sensitive feels overwhelmed by sensory information, but they do not actively try to avoid the overstimulation, instead they may just display frustration. They may be easily distracted, and irritable, cautious, and uncomfortable in loud or bright environments. 

Sensation avoiding: A child that is sensation avoiding feels overwhelmed by sensory information and will actively avoid the stimulation. They may run away from loud, busy environments, cover their ears when overstimulated by noise, or wear gloves to avoid touching certain materials such as paint. 

Hyposensitivity

A child who has low registration for smell, or is sensation seeking may require extra olfactory input (smells) in order to process their environment. 

If a child has a low registration pattern for olfactory processing for smell they may: 

• Be unaware of very strong or unpleasant smells that others notice, such as the smell of exhaust fumes.
• Be unable to label or recognize certain smells.
• Be unaware of the smell of smoke from a fire or other dangerous smells in the environment.
• Be unaware of smells others may enjoy, such as the smell of freshly baked bread. As a result, they may not have a strong preference for the foods that many others may like. 

If a child has a sensation seeking pattern for olfactory processing they may:

• Explore a variety of non-food objects by smelling them. For example, they may smell various people, foods, markers, and toys to explore them. They may also want to smell odors that others would perceive as unpleasant, such as the smell of soured milk or gasoline. 
• Play with feces, due to the strong scent. 
• Crave and actively seek out particular smells, both of food and non-food items. For example, they may be very drawn to a particular flower at the park or the smell of bubble bath. 
• Enjoy eating foods with strong scents such as oranges, garlic, or pickles. 

Case example:

Sarah is a very curious 8-year-old-girl. Her teachers notice that she frequently hovers over the garbage cans in the classroom and playground to smell the contents. When redirected from this behaviour, she will seek out other objects to smell, including classmates. She is having trouble making friends at school because of this, and her parents are very concerned. 

Sarah has a sensation seeking pattern for olfactory processing. She continuously seeks out very strong scents to meet her needs. 

Strategies to assist a child with hyposensitivity for olfactory sensory processing:

• Provide the child with strong scents such as peppermint, citrus, perfume/cologne or use scented laundry detergent. These scents can provide the child with the required amount of stimulation to increase their alertness. You can teach them to use these scents to gain stimulation, as opposed to people or inappropriate objects such as feces. 
• Play games such as “guess that scent.” Try using scented candles, essential oils, or different types of foods and without showing the child have them guess the scent. 
• Create a routine for washing hands, bathing, and cleaning if the child is unaware of their own scent. 
• Provide the child with scented playdough or scented markers. 
• Teach older children strategies to compensate for their hyposensitivity. For example, if they are unable to tell if food has gone bad due to their sensory processing differences, teach them to read expiry dates. 

Hypersensitivity 

Children who are sensory sensitive or sensory avoiding to smells may be considered picky or selective eaters due to a dislike of certain food scents. 

If a child has a sensory sensitive pattern for olfactory processing they may: 

• Become anxious while in rooms recently cleaned with cleaning products, or with air fresheners. 
• Dislike the scent of laundry detergent on their clothing.
• Gag when presented with certain foods or other scents.
• Be anxious about their own scent, particularly if they perceive they “smell bad.” They may want to bathe numerous times a day to remove this smell from their bodies. 
• Become distracted in school because of the smells in the environment. 

If a child has a sensory avoiding pattern for olfactory processing they may: 

• Be a very selective or picky eater, refusing to eat certain foods based on scent. They may refuse to eat certain foods even if they are extremely hungry.  
• Run away from or avoid shared lunch spaces due to the dislike of other lunch smells. 
• Plug their nose when in the presence of particular smells, such as the smell of a flower, perfume/cologne, another child, or food item.
• Refuse to use public bathrooms due to the scent.
• Refuse to go to a particular place, such as a friend’s house because of the smell. 

Case example:

Sebastian is a 5-year-old-boy. Sebastian’s parents are concerned as he will often come home from school with his pants soiled. His teachers have shared that he refuses to use the washroom in the classroom. After discussing with Sebastian, you discover he refuses to use the washroom because of the smell of the air fresheners and products used to clean it. 

From the case, you can see that Sebastian has a sensory avoiding pattern for olfactory processing. He has hypersensitivity towards the scent of the washroom and copes by avoiding this non-preferred scent. He avoids it daily and ends up with soiled clothing. 

Strategies to assist a child with hypersensitivity for olfactory sensory processing:

• In some cases, you can try to desensitize a child to a particular scent by slowly increasing their exposure to the scent. However, be aware that the child may not wish to proceed with desensitization if they become uncomfortable and have a negative emotional response. 
• Use fragrance free cleaning products including laundry detergent. 
• Avoid wearing perfume or cologne or using strongly scented personal care products if you are near the child on a regular basis.
• In class, seat the child away from triggering scents such as the garbage bin. You can seat them next to the window if they are tolerant of the smell outside. This ventilation can help them to cope. 
• Provide the child with a preferred scent, such as an essential oil to use throughout the day if they feel overwhelmed by other scents.