Are sulphites to blame?
'Sulphites' are often the first thing that gets the blame, but this may be more to do with labelling than science. Surprisingly, it is against the law to declare ingredients on alcoholic drink labels except for certain allergens like egg and milk, and 'contains sulphites' for any wine with more than 10 ppm (parts per million).
The process of fermentation itself produces sulphites, so wines that don't contain sulphites are almost impossible to find. There are a few wines that do not contain any additional sulphites but wines like this are difficult to make and keep in good condition so are also relatively rare (see my article 'What are natural wines?' for more on the role of sulphites in winemaking).
The reason for this obligatory label declaration of sulphites is that a small percentage (estimated to be no more than 1%) of the population is sensitive to sulphites, something of particular concern to asthmatics. Symptoms include breathing difficulties and urticaria (an itchy red skin rash) – but not headaches.
One way of testing if it is wine or sulphites that are the problem is to eat dried apricots, figs or pre-prepared salads which often contain considerably higher levels of sulphites than wine. It may be reassuring to know that the European Food Standards Agency is continuing to test sulphite levels in food and drink, and has recently reviewed safe levels of exposure. Its latest findings, published last year, show current permitted levels are acceptable for most consumers and show no concerns about cancer or toxicity, but research is continuing. And it's also worth noting that red wines tend to have lower levels of sulphites than whites as the tannins and pigments act as natural preservatives.
The red-wine headache syndrome
Red wine headache is a symptom that affects some people who cannot tolerate even tiny amounts of red wine. Several possible causes have been proposed and one is the presence of biogenic amines in wine. These are derived from amino acids and can be produced in the body but also by microbial metabolism, and it's this area that is of interest in wine.
A biogenic amine called histamine can cause allergic reactions or intolerance and may be found at higher levels in wines that have undergone malolactic fermentation. The level of histamine varies by wine, and the process of producing it, but red wine has been found to have 20 to 200% more histamine than white.
One reason is that red wine almost always goes through malolactic fermentation but this is not always the case for whites. Oenococcus oeni (aka Leuconostoc oenos) is the species of bacteria that is used in commercial malolactic preparations and this usually produces low levels of histamines.
Are so-called 'natural' wines better for sensitive heads?
But many producers prefer a natural malolactic fermentation and other species of so-called Lactic Acid Bacteria (LAB) found in wine can produce high levels of histamine. So potentially more 'natural' wines may be a higher risk for sensitive drinkers. One suggestion (though take proper medical advice) is to take an antihistamine before drinking red wine to reduce symptoms.
And just to complicate matters, there is some evidence that drinkers who appear to be sensitive to red wine may be deficient in an enzyme called DAO (or diamine oxidase) which breaks down amines, plus for good measure it has been suggested that red wine also inhibits this enzyme.
Another amine that can cause headaches is tyramine, which is found in wine, cheese and other fermented foods. This is also produced by certain LAB found in wine, though its level varies with conditions during fermentation such as sulphite level, pH and nutrient availability.
And what about the congeners?
Another important group of chemical components of wine are the congeners. Congener (which means 'born together' derived from Latin) is a term for by-products of the alcoholic fermentation. This includes important flavour components such as higher alcohols (sometimes called fusel oils for their oily appearance when distilled), esters and aldehydes.
Levels of congeners are typically higher in darker alcoholic drinks such as brandy, rum, red wine and Port gets a 'double whammy' as it's made from red wine with added brandy. Higher levels of congeners are associated with warmer fermentations, exposure to air and oak ageing – techniques which are typical for many red wines. Research suggests that high levels of congeners are associated with feeling worse after drinking. One research paper (Rohsenow et al 2010) compared hangovers after drinking vodka (very low in congeners) compared to bourbon (high congener content). It found similar levels of cognitive impairment between the two drinks but hangover symptoms such as headache were worse with bourbon.
One congener that is implicated in problems with alcohol is acetaldehyde. This can be produced through oxidation of ethanol (for instance during oak ageing) and is also the first breakdown product of ethanol in the body. It is estimated to be 10 to 30 times as toxic as ethanol itself and it has been shown to induce hangover-like symptoms. For some people (particularly of Asian descent) genetic mutations both slow breakdown of acetaldehyde and may produce higher levels in the body too, causing a syndrome known as Alcohol Flush Reaction.
Are tannins implicated in any way?
Another component of red wine that is implicated in the effects of drinking is tannin. Some research suggests that tannins can cause vaso-relaxation or relaxation of blood vessels which is a precursor to headache. Consumption of caffeine before drinking wine is reported to help counteract this effect.
The dreaded dehydration
Many drinkers will recognise dehydration as a feature after a heavy night of drinking. This is because alcohol suppresses a hormone called vasopressin which acts as an anti-diuretic so more frequent trips to the bathroom result. Dehydration may have something to do with the morning-after headache, though it can occur even in drinkers who consume lots of water. Alcohol also may trigger release of cytokines and a reaction against inflammation similar to that of the body battling an infection.
No substitute for being sensible
So of course, sensible drinking is important in avoiding headaches and hangovers but there are also some other pragmatic steps that may help. Drinking plenty of water to avoid the dehydration effect is one. Eating before or while drinking wine also helps to slow down absorption of alcohol and helps the body to keep up with breaking it down. Alcohol is absorbed through the membranes of the mouth, and throughout the digestive system, but peak absorption is in the small intestine. Eating fatty foods in particular delays gastric emptying so slows down the transit to the small intestine.
Reducing the risks
Sadly, if you know you are sensitive to sulphites, or to red wines, then you may have to accept avoiding these products, but choosing paler and lighter drinks, and particularly wines that have little contact with air or oak ageing, may reduce your exposure to some of the components that may cause headache.
Know your limits so you can continue to enjoy one of life's great pleasures – a good glass of wine with friends.