From pets and dust mites to certain foods, common childhood allergies can result in some tell-tale symptoms. By Imy Brighty-Potts.

Knowing when you're allergic to something is important, so you can take steps to avoid a reaction. But when babies and toddlers can't communicate their discomfort like adults would, how can you tell if something might be aggravating them?

Allergy symptoms can range in severity and aren't always immediately obvious - but there are some warning signs to look out for.

Here are five common signs that your baby might have an allergy...

1. Red, weepy eyes

Babies may generally be quite teary, but if they seem to be developing weepy, red eyes that appear itchy and uncomfortable, this could indicate an allergy.

"Allergies to pollen and dust mites can give rise to allergic rhinoconjunctivitis," says George Du Toit, a professor of paediatric allergy at King's College London and consultant at Guy's and St Thomas' hospital. "Upon exposure, such as when petting a cat, the infant may develop red, itchy swollen eyes and swollen eyelids."

2. Itching

Itching is another possible sign of allergies - but how and when the itch presents can vary depending on the trigger.

"An allergic itch will typically come after exposure to an allergen. Young babies are more commonly allergic to food, rather than to air allergens such as pollen or dust mites," says Du Toit. "Air allergies usually take slightly longer to develop, typically presenting at two to four years of age. Children with air allergies tend to scratch more after allergen exposure, such as over the pollen season or after exposure to house dust mite."

You may think your child is a picky eater, but there could be something else at play. As Du Toit notes: "With an itch induced by food, the child will typically not like eating the food as their mouth will itch."

3. Runny noses and coughs

Noticed your little one has a persistent runny nose? "Certain allergies can result in upper respiratory tract symptoms, such as nasal itching, sneezing, runny nose or congestion, and lower respiratory tract symptoms, including cough, wheezing or shortness of breath," explains paediatrician Dr Sanjay Mehta.

It's not always easy to tell the difference between a cold or infection and an allergic reaction. Dr Mehta adds: "Allergic reactions usually happen within a few minutes of exposure to a trigger, although appreciably the trigger is not always obvious.

"Often, fevers during an infection can be a giveaway too, but it is worth noting that the absence of a fever does not exclude a cold. Clear and thin nasal discharge can occur with both, whilst thick nasal secretions usually only occur with infections."

4. Wheezing

Wheezing in a baby can be really frightening, and this can sometimes be a sign of an allergy too. However, always seek immediate medical advice if you spot symptoms like wheezing or shortness of breath, as they may require urgent attention.

"Wheezing is a high pitch whistle sound released on expiration and not on inspiration. Wheezing in children can be acute, intermittent, or chronic," says Du Toit. "Acute wheezing can develop after exposure to a food allergen, or from an air allergen such as exposure to a cat. As well as wheezing, the child may experience sneezing and other respiratory symptoms."

5. Eczema

According to the National Eczema Society, one in five children are affected by eczema - which causes areas of inflamed skin that can become very dry, cracked and sore. While it's not always clear why it develops, it can be an early indicator that a child might be predisposed to allergies.

"Eczema is caused by abnormalities in the outer skin layer and is connected to allergic conditions, such as hay-fever and asthma. It can often be incorrectly attributed to foods, but can actually also be precipitated by irritants, humidity, changes in temperature, stress and infection," says Dr Mehta.

What should you do if you spot these symptoms?

If you think your baby may have an allergy, speak to your doctor. A skin prick test - where a small amount of the suspected allergen is placed on the skin, and then pricked with a needle so it penetrates - can help determine specific allergies. Patch tests and blood tests may also sometimes be used.

It's important to identify any allergies and know how to manage them, which usually means avoiding triggers. This can be difficult in some cases, and things like dust and pet hair and some food allergies can be tricky to navigate. Your doctor will be able to advise on steps you can take, as well treatments and solutions to help deal with any symptoms that might flare-up.