An allergic reaction is the way your body responds to a particular substance or irritant, called an allergen1. Allergic reaction symptoms take many forms and are often mild1. However, they can sometimes prove to be life-threatening2. Read on to explore what an allergic reaction is and the common signs to watch out for. We’ll also cover the 5 potential stages of an allergic reaction, and how long symptoms may last, so you can know exactly what to expect
What is an allergic reaction?
Allergic reactions are a physical response to a specific allergy trigger1. Known as allergens, these substances are typically harmless1. However, your immune system can wrongly treat them as a threat, fighting back with antibodies and histamines that fuel allergic reaction symptoms3.
There are lots of ways for allergens to enter your body. Common entry points include the nose, eyes, mouth, lungs, and skin2. These substances won’t pose a problem for most people who encounter them2. However, if your body overreacts, you might experience a mild or severe allergic reaction as it tries to tackle the issue2.
Allergens take many different forms. Everything from animal dander, pollen and dust to insect bites and natural latex rubber might lead to a sudden allergic reaction4.
How long does an allergic reaction last?
Your allergic reaction time may vary from just a few minutes to several days5. In certain cases, the symptoms could last for up to a month5.
It’ll ultimately vary from person to person, and might depend on5:
How serious the allergic reaction is
The type of reaction you experience
Any treatments that you apply
How strong your immune system is
At the other end of the scale, an extreme allergic reaction could potentially threaten your life6. This is called anaphylaxis6. It can strike very quickly, with dangerous allergic reaction symptoms like swelling and breathing difficulties appearing within minutes6.
Certain medicines, types of food and insect stings can lead to anaphylaxis6.
If you suspect you or someone else is experiencing anaphylaxis, call 9996.
What are the 5 stages of an allergic reaction?
There can be 5 stages of an allergic reaction to keep in mind, but the exact process will depend on your body’s response and how severe the symptoms become5. As a result, not everyone will go through all the stages.
Here’s how an allergic reaction timeline might progress, starting with mild symptoms, all the way up to a major anaphylactic shock.
1. Exposure to an allergen
In the first phase, your body is exposed to an allergen that it wrongly considers harmful1. It releases chemicals like histamines in response, leading to a minor allergic reaction5. Initial allergy symptoms may prove mild and could include an itching sensation or redness5.
2. Further symptoms develop
For some people, allergic reaction symptoms might spread after a few minutes or hours5. Wheezing, hives and congestion are among the possible symptoms during this stage5.
3. Allergy symptoms worsen
n some cases, allergy symptoms can worsen or become more prolonged. Muscle aches, tiredness or headaches could all strike hours, or even days, after initial contact with an allergen5. Skin complaints like itching might continue too5.
4. Anaphylactic shock
In rare cases, things could progress to a more serious allergic reaction called an anaphylactic shock7. This might start with mild symptoms, such as a rash or a runny nose7, but it can quickly escalate to severe discomfort, including7:
A tight chest
Breathing problems
Swelling around the mouth
Sickness
Fainting
A weakening pulse.
Call 999 if you suspect you’re having a serious allergic reaction, such as anaphylactic shock6.
5. Full anaphylaxis
An allergic reaction can become life-threatening once anaphylaxis fully takes hold7. A weak pulse, swollen airways and falling blood pressure are common warning signs. As the blood struggles to flow, the risk of a heart attack rises7.
Call the emergency services on 999 if you experience this stage of allergic reaction6.
Allergic reaction symptoms
Since there are different levels of allergic reactions, the potential symptoms and risks vary. They could prove a mild annoyance, like an itchy allergy rash or sneezing8. However, in more extreme cases, an allergic reaction might affect multiple organs, all over the body9.
Skin reactions
The skin is a common hotspot for allergic reactions. Issues can include contact dermatitis. Here, a particular substance causes eczema to form on your skin10, such as cosmetic ingredients or metals like nickel10. Hives could also appear if your body reacts to triggers like insect bites, particular foods, or medications11. These take the form of raised and potentially itchy bumps or welts11.
Respiratory issues
Allergic reaction symptoms often affect the respiratory system too. They can trigger asthma, for example, where your breathing tubes swell and temporarily narrow12. This then makes breathing more difficult, leading to wheezing, shortness of breath, or a tight chest12. Pollen, animal fur and dust mites are among some of the allergens that could trigger asthma12. You should schedule a GP appointment if you or your child is showing symptoms of asthma, or following an asthma attack.
Gastrointestinal issues
Certain foods have the potential to cause a bad allergic reaction. Your body might disagree with a particular ingredient and respond with allergy symptoms13. These tend to focus on the stomach and digestive system, including13:
• Nausea or dizziness
• Being sick
• Diarrhoea
• Tummy pain
Eye and nose issues
Allergies, such as hay fever, can target the eyes and nose, triggering cold-like symptoms. These could include8:
Red or itchy eyes
Watery eyes
Sneezing
A blocked or runny nose
Other potential symptoms can include tenderness around your eyes and forehead1.
How to tell if you’re having a severe allergic reaction
A severe allergic reaction is called anaphylaxis6. Dangerous or even life-threatening symptoms can appear quickly in response to certain foods, medicines, or insect stings6.
Here are some key symptoms of a severe allergic reaction6:
Breathing difficulties
A swollen throat or tongue
Coughing or wheezing
Fainting or tiredness
Trouble with swallowing
Feeling cold to the touch
The skin, lips or tongue appearing blue, grey or pale
If you suspect that you’re experiencing an anaphylactic shock, call 999 for an ambulance6. The NHS also advises lying down if possible6 and using an adrenaline auto-injector if you’ve been given one6.
Allergic reaction symptoms FAQs
How long does an allergic reaction rash last?
It could depend on the type of allergic rash you have. Contact dermatitis might last for a few weeks in some cases11. Meanwhile, hives may go away in a matter of hours or a few days11.
Are allergic reactions contagious?
An allergic reaction is your body’s unique response to a particular substance it views as a threat1. As a result, it’s not classed as a contagious disease.
How do you stop an allergic reaction?
A range of treatments are available for allergic reactions, which might help to manage or ease your symptoms1. These can include antihistamines, as well as steroid tablets and creams1. Those at risk of a severe allergy reaction might be offered an adrenaline auto-injector, which is a type of emergency medicine1.