The festive season affects people in different ways. If, for example, the words 'Christmas shopping' bring you out in a cold sweat, or the sight of decorated tree before 21 December makes your brow furrow, you probably have a condition called 'being male'.
But thousands of people do genuinely have an allergic reaction to Christmas that, in some cases, increases their risk of becoming seriously ill.
The charity Allergy UK has issued a warning to allergy sufferers to be on their guard this year in case they come into contact with potential triggers.
It has even designed a poster - entitled 'Festive Season Alert' - highlighting the dangers.
Muriel Simmons, chief executive of Allergy UK, told BBC News Online the major problem is that exposure to potential triggers increases sharply during festive celebrations.
That is partly because the heavy-duty socialising in which most people indulge brings them into close proximity to foods, drinks and materials that can set off an allergic reaction.
But it is also fuelled by liberal consumption of alcohol, which means many allergy sufferers are less vigilant about keeping a safe distance from likely triggers.
"People who have a known allergy tend not to be as careful as they should be," said Ms Simmons.
"We are trying to get people to stop and think about what they are doing."
So what are the potential hazards you could face this Christmas?
For anyone with an allergic condition such as rhinitis (runny nose), or asthma, coming into contact with an artificial tree that has spent 12 months gathering dust in the loft can have repercussions.
Artificial trees can make your nose run....
Tiny particles can enter the nose and lungs and trigger attacks of sneezing or asthma.
"Either buy a new tree or get someone else without an allergy to get it down for you," advises Ms Simmons.
"'Take it outside and give a shake or wash it down."
The bad news? Real trees might not be much better.
That is because the sticky sap that they release is also known to spark reactions in people with allergies.
"You can get a runny nose, streaming eyes and a rash on the skin," said Ms Simmons.
"Some people can feel quite poorly and if you are allergic then you don't even have to have contact with it - just being in close proximity is enough."
Some experts suggests spraying the tree down with water before bringing it into the house.
Candles are synonymous with Christmas. But scented candles give off a perfume that can aggravate allergic conditions.
Many women, for example, will complain they react to certain perfumes and stop using them. But when it's contained in a candle, it is difficult to escape.
..but real trees aren't much better
"It can be a nightmare for some people," said Ms Simmons.
"The perfume in candles can spark off rashes, headaches, sickness and asthma.
"Unfortunately, people rarely realise it's the perfume in the candle that's doing it."
Latex allergy has emerged as a major health problem in recent years.
In the NHS, for example, many staff have become sensitive to latex after years of wearing rubber gloves.
In the most severe cases, it can trigger a life-threatening reaction called anaphylactic shock.
Anyone with this condition who comes into contact with decorative balloons can be in real danger.
"I spoke to a lady recently who attended a party where there were balloons stashed on the ceiling in a net, ready to be released," said Ms Simmons.
"Just before they were, she left the room, went down a corridor into another room and shut the door behind her.
"Yet within two minutes of the balloons being released, she suffered a severe anaphylactic shock."
Last year's decorations are a perfect dust trap. But if they are made of any kind of fluffy material, they can also be a great hiding place for the house dust mite - one of the main triggers for asthma.
These thrive on warm, moist conditions and, once disturbed, can spread and aggravate chest conditions.
If it is at all possible, says Ms Simmons, vacuum them as soon as you get them out of the box, or take them outside and shake them.
Ten years ago, peanut allergies were virtually unheard of.
Now, they are commonplace and food labels often carry warnings that products have been prepared in a factory where nuts are used.
But although awareness has increased, says Simmons, Christmas is the peak period for edible nut consumption, heightening the danger.
"There is a much greater exposure at Christmas and for some people it can make life a complete misery.
"Even going to the pub can be difficult as there might be peanuts on the bar."