There's no such thing as an allergic reaction to sulfite.

As someone once observed, that's a bold statement. It's probably the most controversial thing I've ever said, and I say it a lot. And, I’m going to say it a bunch of times, right here.

Sadly, the Internet seems to have become a platform that allows people to be simultaneously incredibly well informed and completely wrong at the same time, especially with regards to things that should have been settled, such as the safety and efficacy of sulfur in winemaking. Just the phrase, 'sulfite allergy' is completely and utterly wrong, without any truth or merit whatever, and yet if you're a winemaker, you hear it all the time.

Are You Sure? Lots Of People Have Sulfite Allergies, Don't They?

Yes I’m sure, and no, nobody has a sulfite allergy, because there is no such thing.

All human beings are more-or-less sensitive to sulfur dioxide, especially the gas form, but nobody can ever be allergic to it. That's not possible for very good medical and physiological reasons, and anyone who uses the phrase 'sulfite allergy' is just plain wrong.
Part of the trouble is that people want very simple answers to complex, interlocking problems. The other, and vastly worse part is that there are opportunistic people out there who are willing to give simple answers, possibly with the idea of selling something or just because they like the sound of their own voices. Me, I like the truth, and the truth is that there is no such thing as a sulfite 'allergy'.
An allergy is an inappropriate immune-system response. Sufferers have excessively active white blood cells: when an allergen binds to the mast cells or basophils they produce antibodies that cause an inflammatory response, which can range from mildly annoying to lethal. Because sulfite is a stable salt of elemental sulfur, it can't cause this immune response, period. It just doesn't work that way, because biology.

To see why this is, let's start by looking at what sulfite is--and is not.

What Is Sulfite?

When winemakers use the word 'sulfite' (or for everywhere except the USA, 'sulphite') they are referring to a form of sulfur, but it's kind of an amorphous term that covers a lot of concepts. It can be

• A stable salt of sulfur, like sodium or potassium metabisulfite
• A measure of free, bound or total sulfur dioxide in solution, usually quoted in Parts Per Million (PPM)
• Sulfur dioxide gas which is sometimes used in commercial wineries
• Some other form of sulfur in wine

As home winemakers we're almost entirely concerned with the stable salt form, used as an anti-oxidant, preservative and anti-bacterial agent, as well as a sanitizer for winemaking equipment. Regardless, all of those things are derived from the non-metal element, sulfur.

What Does 'Salt' Mean?

When people hear 'salt' they think of the white crystals that get sprinkled on popcorn. When a chemist says 'salt', they mean a chemical compound formed between the reaction of an acid and a base. If you're not sure about acids and bases, put some baking soda (a base) in a cup and dose it with vinegar (an acid). This will liberate a bunch of carbon dioxide gas and is mildly amusing.

Salts usually consist of positive ions from a metal with negative ions from a non-metal. In fact, that popcorn salt mentioned above is sodium chloride, a combination of Na1+ (sodium, a metal) and a Cl1- (chlorine, a non-metal).
That salt forms when an an electron is transferred from a sodium atom to a chlorine atom forming a Na+ cation and Cl- anion. This reaction, more vigorous than baking soda and vinegar, binds them together forming NaCl. There's a lot of chemistry we could talk about, valence bonds, octet rules, electrostatic attraction, but the simple thing is that salts happen in nature, because, chemistry.
The whole thing about salts is really important because bonded salts completely change the properties of the the two elements. On their own, sodium and chlorine are incredibly toxic: sodium metal burns and explodes on contact with water, and chlorine is a corrosive gas and the active ingredient in bleach. But combined into a stable salt they're a building block of life, and human beings (and delicious popcorn) wouldn't exist without them.

Why Is Sulfite Used?

Sulfite has been used for thousands of years to preserve food. In antiquity it was found that if you burned sulfur (the yellow powder form) in a tightly sealed grain bin, or inside a barrel, food or wine stored in that container would last much longer than otherwise. That's because burning the sulfur released sulfur dioxide, and that has the properties of:

• Preventing non-enzymatic browning (a complicated reaction related to caramelization, it's what makes wine go from bright red to brick-brown)
• Preventing enzymatic browning (like when an apple slice or ripe bananas go brown)
• Controlling the growth of micro-organisms, like spoilage bacteria.
• Bleaching color out of organic materials (wood pulp for paper is bleached with sulfur dioxide)

Summing up, sulfite inhibits yeast, mold and bacteria, and takes oxygen out of juice and wine. It is added to crushed grapes and juice before fermentation to suppress wild yeast and bacteria, and to wine after fermentation, to prevent oxidation. Sulfite turns out to be so immensely useful that it's in many of the things we touch or consume every day. We have good records that show sulfite has been used since the 1600's in Europe, the 1800's in the USA. It's actually irreplaceable in winemaking, so much so that the French have a standing prize for anyone who can come up with a chemical or a process that replicates the effects of sulfite. The prize stands uncollected after more than a century.

What Was That About Sulfite And Food?

Sulfite is just as useful to food processing as it is to winemaking. pretty much anything that needs to be protected from oxidation has added sulfite. The FDA governs the use and limits of sulfite in the food supply and manufacturers strictly observe those rules.
Here is a partial list of the foods that contain sulfite:
Beer, cocktail mixes, wine, and wine coolers, cookies, crackers, mixes with dried fruits or vegetables, pie crust, pizza crust, quiche crust, and flour tortillas, dried citrus fruit beverage mixes, horseradish, onion and pickle relishes, pickles, olives, salad dressing mixes, and wine vinegar, brown, raw, powdered or white sugar derived from sugar beets, antiemetics (taken to prevent nausea), cardiovascular drugs, antibiotics, tranquilizers, intravenous muscle relaxants, analgesics (painkillers), anesthetics, steroids and nebulized bronchodilator solutions (used for treatment of asthma), canned clams; fresh, frozen, canned, or dried shrimp; frozen lobster; scallops; dried cod, fresh potatoes, fruit fillings, flavored and unflavored gelatin, and pectin jelling agents, cornstarch, modified food starch, spinach pasta, gravies, hominy, breadings, batters, noodle/rice mixes, jams and jellies, shredded coconut, canned, bottled, or frozen fruit juices (including lemon, lime, grape, and apple); dried fruit; canned, bottled, or frozen dietetic fruit or fruit juices; maraschino cherries and glazed fruit, vegetable juice, canned vegetables (including potatoes), pickled vegetables (including sauerkraut), dried vegetables, instant mashed potatoes, frozen potatoes, potato salad, dried fruit snacks, trail mixes, filled crackers, canned soups, dried soup mixes, corn syrup, maple syrup, fruit toppings, and high-fructose syrups such as corn syrup and pancake syrup, instant tea, and liquid tea concentrates.

If you've ever eaten any kind of processed food (i.e., anything not actually pulled out of the ground or picked off a bush) you have consumed sulfite. You've almost certainly consumed it today, if you're reading this after breakfast, because your morning juice had it, or the wheat the bread for your toast was made with it, or your fried potatoes were bleached with it.

How Much Sulfite Is In Food And Wine?

The amounts used are very tiny--that's why they're usually measured in the Parts Per Million range. At the very high end, dried raisins can have up to 1250 PPM of sulfite, but by law dry table wine can have a maximum of 70 PPM FSO2. Because wine made at home isn't shipped or stored like commercial wine, it typically has far less, usually around 20 to 35 PPM.
How much is that in real-world measures? 20 PPM as a ratio would be less than one teaspoon of water added to a 55 gallon drum--a very little amount indeed.

So Why Do People React To Wine If It's Not Sulfite?

(Important disclaimer: I am not a Doctor. None of the following constitutes medical advice and is not intended as a substitute for consultation with a medical professional. If you think you have a medical issue with anything you consume, please consult your family physician--and never, ever someone on the Internet, not even me. On the other hand, all of the following is scientifically proven information. Just not Doctor-licious.)

Standard Response

It depends on what reaction you're talking about. If it's happiness, relaxation and a sense of joyfulness and fulfillment, then you're probably doing it right. If it's headaches, fatigue, nausea and misery the next morning, it's probably an issue of over-consumption.

Mild Unpleasantness

If it's redness of the face, slight dizziness and loss of equilibrium combined with sweating and a desire to sing karaoke, it's almost certainly an issue of alcohol dehydrogenase deficiency. The human body detoxifies alcohol in a two-step process. The first step is when the alcohol is attacked by alcohol dehydrogenase, which breaks it down into aldehydes or ketones. This is good, because if your body didn't break down the alcohol you'd be drunk for the rest of your life.
But it's also bad, because more than a little aldehyde in your blood is worse than alcohol. Aldehyde is pretty much nail-polish remover. Fortunately, your body has that all lined up, and another complex of enzymes called aldehyde dehydrogenases that break it down, eventually converting it into energy the body can use.
But you may belong to a sub-group of people who have less aldehyde dehydrogenase than others, and so you get stuck in between the two biological processes, with the equivalent of nail polish remover circulating in your bloodstream. People of northern European descent seem to have more aldehyde dehydrogenase than average, while people from southeast Asia can have less--keep in mind individuals and groups vary in their response, but most of us have a friend who gets flushed and tipsy almost immediately after consuming even a small amount of alcohol--this is the likely cause.
The best treatment for it is to consume alcohol carefully, and within your tolerance, and be sure to consume plenty of water along with your drinks. And remember, karaoke is never a good idea.

Headache, Stuffy Nose, and More Serious Symptoms

Here's a surprise: these symptoms are almost certainly caused by an allergic response. But it's not sulfite. It's a biogenic amine response.
Biogenic amines are compounds made by microbial, vegetable and animal metabolism. They're found in all foods containing proteins or free amino acids, including fish, meat, dairy, wine, beer, vegetables, fruits, nuts and chocolate. In general, all fermented products contain biogenic amines. One really important biogenic amine is histamine, which is a neurotransmitter that signals and inflammatory response from mast cells. It's the reason why people take anti-histamine drugs.

Some wines have more--a lot more--biogenic amines than others. In particular, any wine that has been through the process of malolactic fermentation (MLF) will be loaded with them.
MLF is not actually a fermentation. It's actually a bacterial conversion, where a bacteria, usually one introduced by the winemaker, converts malic acid in the wine into lactic acid. This is done for three reasons:

• If you don't do it deliberately it can happen spontaneously, which would ruin bottled wine.
• If converts harsh-tasting malic acid into smoother lactic acid
• It produces diacetyl, a chemical that smells like melted butter or buttered popcorn
• That's all well and good, but a by-product of most MLF is a lot of biogenic amines--and therefor a lot of allergic response. Sulfite is not the culprit.

And we can actually build on this with another significant data point: people who suffer from allergy response to wine will often state they can drink whites: that it's mainly red wine that affects them, and that wine made from kits doesn't affect them at all. The takeaway here is that almost all red wines go through MLF, while it's usually only Chardonnay that gets MLF in whites, but red wines have far less sulfite than whites (the tannins help prevent oxidation, so they need less sulfite to protect them) and kit wines never go through MLF--it can' t be successfully done with most of them, no matter how hard you might try.

What About Sulfite-Free And Organic Wine?

The simple truth is this: there is no such thing as sulfite-free wine. All wine contains sulfite, even when the winemaker adds none. That's because yeast make sulfite as a by-product of their metabolism, so even 'no sulfite added' wine contains 10 PPM of sulfite. If someone can drink it, they can drink any other wine with sulfite in it.

What About Sulfa Drug Allergies?

Sulfa drugs are classified as sulfonamides, and don't have anything to do with sulfite or elemental sulfur. It's like saying you're allergic to penicillin, so you can't use pencils--not related.

What About Asthma Attacks From Sulfite?

The gas coming off of a liquid sulfite solution (metabisulfite powder dissolved in water) is sulfur dioxide, and is quite irritating. When it comes in contact with moisture (such as the mucous membranes in your lungs) it forms sulfuric acid. This is especially dangerous for people with asthma, as it can trigger attacks, but it's not an allergy.

What Should Concerned Wine Lovers Do?

Humans have been drinking wine for at least ten thousand years, and for every one or those years the wine has--always and without exception--contained sulfite. Sulfite is very safe, effective and useful in a well-made wine.
If you have a concern about your health, always consult your physician.
If like me, you regard wine as a delicious, healthful and gracious part of a life of joyfulness and abundance, then be of good cheer. If commercial wines give you symptoms, I suggest making your own. There will be far fewer biogenic amines, and you'll be able to control everything that goes into it--and if you want, you can even leave the sulfite out to suit yourself (just don't expect a warranty on that . . . ). And you'll have the added benefit of making something wonderful to share with your friends and family.
One of my favorite people ever once told me, 'Wine is a playground, not a prison. Enjoy it in all the ways that you can.' Get out there and play.