Sensitivity and allergy to inhalants can be subtle, such as a catch in your throat when you breathe in a certain aroma to life-threatening anaphylaxis and everything in between. While most people experience that catch in the throat after inhaling, say, ammonia, some are sensitive to perfumes, essential oils and scents in everything from air fresheners and candles to dryer sheets and laundry detergent. The key to determining whether you are experiencing an allergic response rather than response to toxic fumes or just a smell you find unpleasant is to classify your symptoms objectively. Does your nose run or do your eyes water? The cause is likely to be either toxic fumes or an allergy—and most people are aware of what fumes in and around households and other public places might be toxic. Ammonia, toluene and chlorine, all toxic in concentration, come to mind as common substances used in cleaning solutions. Breathing these fumes too closely will interfere with your respiration and you are soon driven away from the source. However, if the response is triggered by the scent of a candle or air freshener, you are more likely to be allergic to it. If you do not like the smell but no physical reaction comes from it, then it is merely a personal preference.
Animal dander is also frequently an allergen that enters your body as inhaled particles. Allergy to animals can either be because of inhalants or contactants, and sometimes both. Most people who have animal allergies are sensitive to only one or two types of animals rather than all of them. Animal lovers who find themselves allergic to dogs might consider a cat, or vice versa. Hairless animals also have dander or deposit saliva on their skin when cleaning themselves, or secrete oils to which some people might be allergic. Even fish in an aquarium or bowl may subject the owner to allergens when cleaning the container.
Certain inhalants, such as the ever-present but largely invisible air pollution surrounding large cities, may either be odorless or you may have developed a tolerance for the odor such that you no longer consciously smell it. It is even more frustrating to find yourself with symptoms that indicate allergy but with no perceptible cause.
Technically, this class of foreign substance most often has to do with the poisons of insect stings and bites, which you usually receive in such small doses that only a mild itch or reddening occurs. It is when your reaction to the sting or bite is extreme, often causing a serious case of hives or anaphylactic shock, that you would say you are allergic to the toxin. Frequently it is a case of receiving several stings or bites within a few moments, such as when a swarm of bees attacks, that causes an allergy to develop. Unfortunately, this can occur so rapidly that the very first allergic response may result in death. If you have ever developed even a mild case of hives or found yourself gasping for breath after receiving stings or bites, it is imperative to carry emergency epinephrine when you are out-of-doors.
Another source of injected allergens is medication that is hypodermically delivered. In some cases, the medication is toxic and is introduced to combat an even more dangerous illness. It is again when the reaction is extreme, beyond that which most people experience in response to the toxin, that it would be identified as an allergy. An example would be a pain medication that makes most people drowsy and perhaps a little queasy. The person who reacts with violent, projectile vomiting to any amount of the same medication would be said to be allergic to it.
This is another class of allergens that consists of both natural substances and those that have been artificially manufactured. Natural allergens include plant fibers such as wool, other animal hair or fur, oils from certain plants (including the toxic oils of poison ivy, oak and sumac) and metals, most frequently nickel or precious metals that have been strengthened with nickel, such as silver and gold jewelry. Other contactants that may cause allergic response include ingredients of soaps, detergents and cosmetics—anything with which your skin comes in frequent contact. Symptoms of this type of allergy are most often rashes, although other symptoms such as hives or infections may occur.