We all get run down at some point – having that 'viral' feeling, catching one cold after another, constantly feeling tired and washed out.

Your body's immune system is its natural defence against infectious diseases and illness. These defences fight off disease-causing microbes (pathogens), such as bacteria and viruses. Having a weak immune system will put you at greater risk of infections and illnesses.

You can support your immune system by following a healthy diet and lifestyle and if you are deficient in any vitamins by taking supplements.


Lifestyle factors can contribute to a weakened immune system, including: smoking; drinking alcohol; emotional stress; lack of sleep; not getting enough exercise; and ageing. Illnesses such as cancer also weaken your immune system.

Poor diet and lack of sunlight in winter can lead to deficiencies in certain vitamins and minerals needed for healthy immune function.

Vitamin D plays an important role in immunity and helps to activate T cells, which are part of the immune system responsible for reacting to, and fighting off, bacteria and viruses. A 2016 study found older people in long-term care given high doses of vitamin D3 monthly were 40 per cent less likely to suffer from acute respiratory illnesses. A study published in 2017 in the British Medical Journal found daily or weekly vitamin D supplements halved the risk of respiratory infections in people with the lowest levels of the vitamin. In people who had higher vitamin D levels, supplements cut their risk of an infection by 10 per cent.

Taking certain medications can, after a period, weaken the immune system. Steroids, also known as corticosteroids, are anti-inflammatory and as well as reducing inflammation in the body, they also inhibit the function of the immune system. Chemotherapy drugs used in cancer treatment can also weaken your immunity.


Symptoms of a low immunity include frequent, persistent and recurrent illnesses and infections – and slow recovery.


If you're worried about your immunity, speak to your GP who will assess your symptoms, medical history and lifestyle factors. They may also do some blood tests to check levels of iron and other vitamins and minerals, as well as hormones, and identify how well your organs are working.

Who gets a low immunity?

It's possible for anyone to suffer with low immunity at one time or another. A study, published by Nature Communications, found that there's an increase in immune defences during winter, which protects against infection but also raises inflammation levels, making the body more vulnerable to other conditions such as heart disease, psychiatric and autoimmune diseases.

The flu vaccination is recommended for people who have long-term, chronic, health conditions; pregnant women; the over 65s; and children aged under two, and those in primary school up to year three.


A healthy, well-balanced diet full of vitamin C-rich, fresh fruit and vegetables, is important for immunity. One study found that individuals under short-term extreme physical stress who took vitamin C supplements halved the common cold risk. Vitamin C is also shown to increase white blood cells. Good sources of vitamin C include fruit and vegetables, such as oranges, red and green peppers, strawberries and blackcurrants. Alternatively, take a supplement. Garlic may also be used as an immunity booster due to its anti-bacterial and anti-viral properties. One Cochrane study assessed 146 participants over three months and found that those who took garlic every day had fewer colds, compared to a placebo. Garlic can be taken as a supplement if you dislike the taste.

It's also important to take a vitamin D supplement if you don't get enough sun exposure and to eat good dietary sources, such as eggs, salmon and sardines. Public Health England (PHE) now recommends everyone aged one and over need 10mcg of vitamin D a day and advises some people may want to take a supplement, particularly during autumn and winter.

PHE also recommend those aged over 65; pregnant or breastfeeding women; people with inadequate exposure to sunlight (including those who cover their bodies with clothing for cultural reasons or live in residential care homes); and people of African, Afro-Caribbean or south Asian origin may want to take a supplement all year-round.

Perlargonium is available in the UK as registered traditional herbal medicine (THR) to relieve the symptoms of upper respiratory tract infections including the common cold.

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