Whether you've worn new shoes, different socks, been for a long walk, or run in ill-fitting footwear, you may not have happy feet afterwards.

Friction and pressure caused by repeated rubbing from badly-fitting footwear and socks, and too much moisture between the foot and sock, can cause painful blisters.

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The fluid-filled sacs can also be caused by foot deformities, and can particularly afflict people with existing conditions like diabetes.

What happens

A spokesperson for AXA PPP healthcare explains: "Blisters begin as small pink spots caused by friction or pressure, turning white as they worsen. Fluid collects under the damaged skin to cushion the tissue underneath, and new skin eventually begins to grow there.

"Most blisters heal naturally after three to seven days if further friction is avoided. The body slowly reabsorbs the fluid inside the blister and the white skin on top dries and eventually peels off.

"However, if the blister turns yellow or green, or the skin around it becomes red and inflamed, it may be infected and need medical treatment.

"After a blister bursts, it's best to leave as much skin around it as possible, to act as a natural bandage as the area heals."

[Read more: Try toothpaste to dry blisters out]

How to prevent blisters

There are plenty of things you can do to avoid getting blisters. The Society of Chiropodists and Podiatrists suggests:

1. Wear comfortable, well-fitting footwear, especially on long walks or runs.

2. Wear good walking socks in the correct size. Look for socks made of fibres with good ‘wicking’ properties.

3. Try wearing socks inside out to prevent the seams rubbing.

4. Try wearing special ‘dual layer’ socks, which eliminate friction at the skin surface.

5. Change to fresh socks if they become damp.

6. Keep toenails short.

7. Remove any foreign bodies from your socks and shoes.

8. Ensure the tongue and laces of your shoes/boots are arranged correctly and evenly.

9. Check feet carefully and regularly for any sign of rubbing and tenderness.

[Read more: Why exposed toes are no-no’s: The reasons we hate feet]

If you get a blister

Act immediately if you feel any friction or discomfort: blisters can form very quickly.

Emma Supple, podiatrist on behalf of Flexitol Heel Balm, recommends: 

"If you get one, proceed with caution. Podiatry advice is to pop the blister and allow the roof of the blister to press down on the damaged skin and heal the area.

"Do not pick the blister as this will make it very sore, and opens the area to infection and delays healing. It's best to sterilise a needle with a match, then pop the side of the blister. Expel the fluid and then apply a dry dressing on the top.

"If blisters burst themselves, then use an antiseptic cream to soothe and apply a large plaster. The area will be vulnerable to further trauma so make sure to protect the area with a plaster."