Sometimes allergies are portrayed as jokes. Daniel Jackson's is - jokes like when they send a box of tissues through the gate and receive a reply "send more." There has also been an instance on this show of the cure to a disease being an antihistamine.
In Shira Glassman's Mangoverse, the queen has food sensitivities.
Allergies can also be found in literature for children, which might be a place that hard-core genre readers aren't reading a lot. Sometimes it takes the form of "You can't have adventures because ____".
Allergies can be very serious, utterly life-changing, and life-threatening. Something like asthma could totally change your plot. Food allergies could feature in a story about first contact.
There are some allergies in Star Trek. Kirk was allergic to eye medication. Jedzia Dax had a kind of juice that would make her spots itch. Wesley was allergic to a pain medication.
Reggie speculated that you could write something really interesting about an amphibious world where humans needed life support because they were allergic to everything.
We remarked on how our memories elide things from our familiar narratives, as when allergy situations occur but we don't notice them. This link has a truly impressive list of contexts in which allergies appeared in Star Trek, most of which I had no memory of.
Do we need something to be a pivotal piece of the main plot in order for us to remember it?
Climate change is causing people's allergies to get worse.
People who are terraforming a planet should be expected to have allergic reactions.
One novel that takes on the question of allergies in an interesting way is Mira Grant's Parasite, discussed at this link. A company has engineered parasites that keep people from having allergies and provide other benefits, but which have certain terrifying side effects...
Symptoms of allergic reactions can range widely, including hives (urticaria), itchy eyes or hands, nerve pinches, systemic inflammation, neuralgia, chronic pain, eczema, in addition to runny nose, asthma, and sneezing. Reggie knew someone who had a dairy allergy misdiagnosed as fibromyalgia. Che mentioned that allergies can also have emotional side effects. They can even cause malabsorption of other nutrients.
People can also be allergic to metal. Some people have super-corrosive sweat, such that they can even leave fingerprints on stainless steel. A study on it can be found here. When the metal breaks down in contact with the skin it can cause painful rash.
We discussed the hygiene hypothesis, which suggests that an increase in allergies may be caused by a reduction in the number of pathogens that our immune systems have to deal with. The immune system doesn't "have enough to do," the hypothesis goes, so it attacks odd substances. Lower allergies in certain groups of humans have been linked to exposure to parasites. People who are exposed to pigs, or even to some pets, will have fewer allergies.
There was a period when my own kids were small when doctors would advise parents not to expose their children to certain types of foods until a certain age - strawberries until age one, for example. The purpose of this advice was to reduce allergies, but it was later found that this advice had the opposite effect.
Serious allergies have been treated with controlled exposure to the substance the person is allergic to.
Another possible effect of an overactive immune system is autoimmune disease.
There are a ton of story ideas that came out of the discussion:
What would first contact be like if humans were allergic to the species they're encountering? We hypothesized that intermarriage would be out. Kate said the aliens would think "humans make exploding sounds and emit liquid in mist form." Reggie remarked that it would be very easy for some people to spin an adverse reaction as intentional harm. We imagined what a fantasy epi-sword might be (as opposed to an epi-pen). Kat thought of a context where a person recognizes an allergic reaction but meets resistance when they try to stop it because of a clash of medical practices. A society more advanced than ours would consider our medical practices barbaric. What if a potter were allergic to clay? Che noted that she knows a dollmaker who is allergic to resin and does her work in a hazmat suit.
Thank you to everyone who contributed to this discussion! Today's hangout meets in one hour to discuss Children; I hope you can join us.