Can peanut dust make you sick? If someone’s eating a peanut butter sandwich next to you in the cafeteria, can that make you sick? What about airborne particles from other foods . . . do they pose a danger? The short answer to these questions is yes, airborne allergens can affect people who are sensitive to those allergens. In some, relatively rare cases, airborne allergens can induce severe reactions. The level of risk, however, requires a somewhat longer answer.

Whenever someone cracks open a peanut, tears open a package of powered milk, kneads bread dough, or fries a fish, allergens can take to the air and travel across a room where unsuspecting food allergy sufferers can inhale them. Although these situations commonly occur, serious reactions from airborne exposure are not terribly common, though they can and do happen.

The trick to dealing with such situations is to acquire the skills for differentiating between situations that pose a real risk and those that pose little or no risk. The risk of experiencing an airborne reaction varies greatly depending on the concentration of food protein in the air.

And this hinges on how the food is handled, how close you are to the food being handled, and how confined a space you’re in. With peanuts, for example, you face four levels of risk.

Level-one risks arise when someone is eating a food next to you that contains the allergen as part of its ingredient; for example, a peanut butter or grilled cheese sandwich. In this instance, the risk that food protein becomes airborne and causes a reaction, especially a severe reaction, is extremely low.

Even though you can smell the peanut or cheese, the scent arises from aromatic oils and has nothing to do with the protein that triggers a reaction.

Not enough peanut or milk protein emanates from that sandwich to put you at any real risk, and reactions with this type of exposure are rare, even if you are in close proximity to the sandwich eater. (For a first-hand look at the comparative dangers of inhalation risks from peanut.)

One step up from level one are level-two risks; for example, you’re on an airplane where your fellow passengers are tearing into their tiny bags of peanuts. In this case, small amounts of peanut dust, which does contain the protein, may become airborne, especially since the bags of peanuts are being opened in the negative-pressure environment of the airplane cabin.

The risk may further increase because you’re in close proximity to the peanuts, you’re in very confined space, and the air’s re-circulating, potentially making matters worse. Severe reactions have occurred on airplanes that appeared to be due to this airborne exposure, but you have to put the risk in perspective:

• Tens of millions of people with peanut allergy have flown with peanuts being served on board, yet only a very small number of people have reported reactions.

• If the risk were high and planes were routinely making emergency landings due to allergic reactions, they would have stopped serving peanuts a long time ago.

• As someone with a serious peanut allergy, I have flown thousands of times with no reactions.

Several major airlines have stopped serving peanuts to address the concerns of their passengers who have peanut allergy. The decision to go peanut-free is more for public relations reasons than to reduce the true allergy risk. I tell my patients to arrange for peanut-free flights, at least for their peace of mind, but personally, I don’t spend a lot of time looking for peanut-free flights when I travel.

Risk levels three and four occur when people are shelling peanuts around you. This clearly causes more disturbance and a greater likelihood that peanut protein can become airborne, especially when the peanut shells cover the floor around you and people are walking on them, kicking up more dust.

The key features that differentiate risk levels three and four are the proximity to the peanuts and, more importantly, how confined the space is, as demonstrated in the following two examples:

• Level-three risk: In an outdoor environment — for example, a baseball game — reactions are very uncommon because the allergen is swept away very readily by the open air.

• Level-four risk: In an indoor space, especially a small space like the waiting area of a restaurant, the risk of reactions rises dramatically.

Allergens In Cooking

When you’re cooking at home, you have control over what you cook and how you cook it. By following the precautions, you’re safe in your own home. When you go out to eat or drop in at your local coffee shop, however, the risks of experiencing an airborne reaction increase.

Food allergists commonly see reactions triggered by the cooking of eggs, fish, and shellfish, especially on an open stove. To reduce the risk, take the following precautions:

• Steer clear of the cooking area. If you’re eating dinner at someone’s house, stay in another room while your host prepares the meal. If you’re in a restaurant with an open kitchen, sit at the table farthest from the open area.

• Run an efficient ventilation fan. Of course, you don’t have any control over this at a restaurant, but if you’re at someone else’s house, you can ask them to turn on the exhaust fan.

• Tell people about your food allergies. When eating at someone else’s house, let them know what you’re allergic to. Most friends and family members are willing to adjust the menu if they know what to do.

Remain vigilant of possible exposures from cooking and food preparation. In one week alone, I saw two patients who experienced airborne reactions at restaurants. One patient reacted in a restaurant with an open kitchen (the server unfortunately seated the family right next to the kitchen).

Another patient, a curious two-year-old with milk allergy was allowed to sit on the counter at a coffee house and watch them froth the milk for his mother’s latte. A few minutes later, hives erupted on his face, presumably appearing where microscopic droplets of milk landed on his skin. As with contact reactions, inhalant reactions typically are not severe.

They most often begin with a rash or hives on the face, itchy eyes, or a runny nose — places where the airborne food comes in contact with the body. In most instances, you can quickly recognize the early symptoms and flee the scene (or at least move away from the cooking area) to halt the progression of symptoms. The severity of a reaction is usually in direct proportion to the level of exposure.

Severe airborne reactions primarily occur in the following situations:

• You get a huge dose all at once. For example, if you have a severe wheat allergy and walk into a bakery where hundreds of loaves of bread are being made, this huge single dose of allergen may trigger a severe reaction even if you immediately exit.

• You can’t leave. If you’re on an airplane, you can’t just get up and walk off the plane.

• You won’t leave. Sometimes people are too stubborn or embarrassed to leave. I’ve seen a patient with a fish allergy take a new job as a dishwasher in a seafood restaurant. I’ve also seen a number of teenagers who knew they were beginning to react but didn’t leave the party where their friends were eating mass quantities of peanuts.

Be sensible about the risks, remain aware of your surroundings, and be prepared to take action when you observe serious risks, but don’t let your food allergy run (and ruin) your life.