Autumn is well and truly here and for plenty of us that means weeks of on-off sniffling, sneezing and feeling under the weather.

But it’s not always colds and flu that are to blame.

The onset of cold, damp weather brings the indoor allergy season into full force for at least 12 million people, according to Allergy UK.

The charity’s clinical director Maureen Jenkins explains: “At this time of year we spend more time indoors with the windows shut, increasing our exposure to potential allergy triggers such as house dust mites – microscopic creatures that live in beds, carpets and soft furnishings – moulds that thrive in damp conditions, and even our pets.”

Add in mould spores growing on rotting leaves and autumn is the perfect storm for allergy sufferers.

“Symptoms can include a runny nose, itchy eyes, repeated sneezing, wheezing and coughing, which is why people may mistake them for a cold. ­Exposure to allergy triggers can also make asthma and eczema symptoms worse,” adds Maureen.

An allergy is the result of your body’s immune system going into overdrive.

It mistakes a ­harmless substance, such as mould, skin cells from your pet or house dust mite droppings for something harmful like a virus.

It then launches an attack, producing substances called histamines, which cause the symptoms.

Allergies overall are increasing at 5% a year, affecting one in three people, according to Allergy UK, and you can develop ­symptoms for the first time at any age.

Here’s what to do if it happens to you.

Find the culprit           

Your pharmacist can help determine whether it’s a cold or an allergy, says Boots pharmacist Angela Chalmers.

“With a cold you may feel achy and feverish, getting gradually worse then better. With an allergy, there’s no fever and ­symptoms can come and go for weeks.

They often involve ­repetitive sneezing rather than the one-off sneezes you get with a cold. You may also notice symptoms are worse in certain ­environments like home or in the garden.

If the trigger isn’t obvious your GP can do a blood test for specific allergic ­triggers such as house dust mites or mould. Once you know the triggers, try to avoid them.

Go smoke free

Cigarette smoke aggravates inflamed skin and membranes in your nose, windpipe and lungs, making symptoms worse, so don’t let anyone smoke in your home.

For help ­quitting, visit www.nhs.uk/smokefree .

Blitz your bed

The average single mattress harbours two million dust mites while a pillow can double in weight over six months due to dust mite droppings. Yuck!

To kill off dust mites, sheets must be washed at 60C.

Leave the covers pulled back during the day and regularly vacuum your mattress, pillows and soft ­furnishings.

You can get allergy-friendly mattress covers, which create a barrier, depriving mites of food and ­moisture.

But make sure you buy products that have been tested. Look for the Allergy UK Seal of Approval. Check out approved products at allergyuk.org.

Wage war on dust

Have as few soft ­furnishings and carpets as possible and choose roller blinds or washable curtains.

Dust with a damp cloth and vacuum regularly. Look for a vac with a HEPA filter, which traps even the tiniest particles.

Beat humidity

Dust mites and mould thrive in humid environments.

“Open windows regularly, especially in the bathroom, and if possible use extractor fans after showering or cooking to avoid condensation,” advises Maureen.

“Avoid drying clothes over a radiator and remove mould around window sills with a weak bleach solution.”

Be plant aware

“Potted house plants can release mould spores so remove the top soil regularly or cover with pea shingle,” says Maureen.

Wear a mask to rake up leaves or grass. Better still, ask someone else to do it for you.

Detect damp

Damp isn’t always obvious. It can lurk behind wallpaper and under floors if there’s been a leak that hasn’t dried out.

It’s a serious health threat and can lead to hard-to-treat fungal infections in the airways. If you’re a home owner, contact a specialist damp company. If you rent, tell the landlord.

Banish pets

Keep pets out of the bedroom and ­regularly wash and groom them.

An air purifier that traps allergens may help but check which allergens it captures.

Asthma UK suggests choosing one that’s ozone-free as ozone can make asthma worse. If ­symptoms are severe, you may have to consider rehoming your pet.

See your pharmacist

Try a non-drowsy, over-the-counter antihistamine such as Benadryl Allergy Relief, £3.99 for 12, Superdrug.

For a runny nose and sneezing, try a steroid nasal spray such as Boots Hayfever Relief 50mcg Nasal Spray, £7.29.

“Most people don’t use nasal sprays correctly – your head should tilt downwards rather than back,” says Maureen.

Build barriers

If you’re pregnant or want a drug-free product, try a barrier balm such as Hay Max, made from beeswax and sunflower oil, which traps allergy-causing particles before you can breathe them in.

It costs £6.99 per pot, from pharmacies, ­supermarkets or visit haymax.biz.

Protect your skin

“If you have eczema, use ­lukewarm water when washing, pat skin dry gently and apply emollient cream. Apply this four times a day during a flare-up – ­ointment may be better for broken skin,” advises Angela.

“Glide the cream in the ­direction of your body hair rather than rubbing in circles, which can further irritate the skin.” Try Boots Derma Care Emollient Cream with almond oil and lanolin, £5.89 for 325g.