Is It a Cold or Allergies? What Are the Differences?
Allergies and colds cause similar symptoms, but the causes and treatments are different. Both cause upper respiratory symptoms such as coughing, congestion, and sneezing. Both can make you feel miserable and have symptoms that last for more than a week. Neither can be cured with medications, but medications can help the symptoms and make you feel much better.
Unlike colds, allergies are not contagious. However, they do have seasonal peaks, and that can help differentiate them from colds. Understanding the differences between allergies and colds is important to determining when to see a telehealth doctor.
Colds are caused by one of the over 200 different respiratory viruses that pass between people, especially in the fall and winter. Scientists will commonly classify these viruses into six families:1
- Respiratory syncytial virus
The viruses that cause the common cold, or, more properly, nasopharyngitis, are spread by aerosol transmission. When you have a cold and cough or sneeze, microscopic liquid, solid or semisolid particles are transmitted into the air. They are so small that they stay suspended in the air. Talking, breathing, singing, sneezing, and coughing can all expel these particles into the air.
Aerosolized particles can stay suspended in the air for hours, especially in poorly ventilated rooms. When you enter a room that contains these aerosolized particles and breathe them in, you can get an infection.
When a person with an infection coughs or sneezes, they also expel droplets. If you touch a surface covered in these droplets and then touch your eyes or nose, you can also get an infection.
The best way to protect yourself from getting frequent upper respiratory infections is to wash your hands often, not touch your face, stay away from infectious people, and avoid poorly ventilated public spaces.
Cold symptoms are generally mild, but they can make you feel miserable for a week or so. Common cold symptoms include:
- Runny nose
- Nasal congestion
- Low-grade fever
- Sore throat
- Irritated, itchy throat
- General achiness
Your immune system protects you from pathogens. Sometimes your immune system can overreact when it encounters benign foreign substances called allergens. This overreaction causes the symptoms associated with an allergic reaction.
Allergens can enter your body through your nose and mouth, be injected, or be absorbed through the skin.
When an allergen comes into contact with your immune system and causes a reaction, your body will put up a defense. Mucous membranes in your eyes, nose, mouth, and gastrointestinal tract will start producing tears, mucus, and saliva to wash away allergens. Increased histamine will dilate blood vessels and cause redness, swelling, and itching.
Depending on how severe your immune reaction is to an allergen, your symptoms may be more of a nuisance or life-threatening and severe allergy symptoms.
Allergy triggers can be divided into respiratory allergens, food allergens, and other allergens.2
Common respiratory allergens:3
- Pollen: ragweed, plantain, timothy grass, ryegrass
- Dust mites: T. putrescentia, D. farinae, D. pteronyssinus
- Animal dander: cat, dog, horse, feather
- Fungal spores: Aspergillus, A. alternata
Common food allergens:
- Fish and shellfish
- Insect stings
Allergy symptoms are usually in response to histamine, a chemical your body secretes to protect itself from threats, whether dangerous pathogens or benign allergens. Histamine dilates blood vessels and increases blood flow to the area of your body where the allergen is trying to enter—mucus and tear production increases.
Common allergy symptoms include:
- Itchy eyes, nose, and throat
- Runny nose
- Tingling sensations
- Swelling of lips, tongue, face, or throat
- Swelling at the sight of an insect bite
- Stomach cramps
- Chest tightness
- Feeling faint
Anaphylactic reactions are severe allergic reactions that can be life-threatening and require emergency treatment. If you have wheezing, difficulty breathing, facial swelling, or feel faint, seek emergency help.
If your cold has persisted longer than a week or if your symptoms improved and then worsened, a telehealth appointment with a doctor can help determine whether you have a secondary bacterial infection.
While cold symptoms caused by viruses are treated with medications that treat symptoms, worsening symptoms, or bacterial infections may require a prescription medication. Sinusitis, an infection of the sinus cavities, is a common secondary infection people get after having a cold. Sinusitis, when thought to be caused by bacteria, is treated with antibiotics.
If you have chronic allergy symptoms, make a telehealth appointment to learn more about allergy treatments that help control your symptoms and make you feel better.
While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.
1. Grief SN. Upper respiratory infections. Prim Care. Sep 2013;40(3):757-70. doi:10.1016/j.pop.2013.06.004
2. Lei DK, Grammer LC. An overview of allergens. Allergy Asthma Proc. Nov 1 2019;40(6):362-365. doi:10.2500/aap.2019.40.4247
3. Krilis S., Baldo BA., and Basten A. Analysis of allergen–specific IgE responses in 341 allergic patients, associations between allergens and between allergen groups and clinical diagnoses.Australian and New Zealand Journal of Medicine. 1985;15(4):421-426. doi:https://doi.org/10.1111/j.1445-5994.1985.tb02764.x