Allergies, Cold, Flu, or COVID? How to Tell the Difference

Did you know?

• All four conditions—allergies, colds, flu, and COVID-19—can cause congestion, fatigue, and coughing.
• But only one is triggered by your immune system reacting to harmless substances.
• And only one can cause a sudden loss of taste or smell.

These conditions share many symptoms, which is why confusion is common, especially during fall and winter.

Knowing the difference matters because treatments vary: antihistamines work for allergies, but they won’t help with the flu or COVID. And while colds usually just need rest and fluids, flu and COVID can sometimes require medical attention or prescription antivirals.

Being able to recognize patterns in symptoms makes it easier to choose the right care, protect others, and know when to see a doctor.

Allergies: Triggered by Your Environment

Allergies happen when your immune system overreacts to things like pollen, dust, or pet dander. These aren’t infections, so you won’t get a fever or body aches.

Common symptoms:

• Sneezing
• Runny or stuffy nose
• Itchy or watery eyes
• Scratchy throat

Key differences: Allergies don’t cause fever, body aches, or sudden exhaustion. Symptoms show up repeatedly around triggers and often follow a seasonal pattern.

Seasonal allergy patterns

• Spring (March–May): Tree pollens
• Summer (June–August): Grass pollens
• Fall (August–October): Weed pollens, outdoor mold
• Winter: Indoor triggers (dust mites, pet dander, mold)

Treatment: Focus on avoidance and symptom relief. Options include antihistamines (e.g., cetirizine, loratadine), nasal steroid sprays (e.g., fluticasone), decongestants, and immunotherapy for severe cases. Over-the-counter remedies like saline rinses can help.

Common Cold: Mild and Short-Lived

Colds are usually caused by rhinoviruses and are among the most common illnesses in the U.S. Most people recover at home without complications.

Typical symptoms:

• Runny or blocked nose
• Sneezing
• Sore throat
• Mild cough
• Low-grade fever (especially in kids)
• Mild fatigue

Onset and duration: Symptoms start 1-3 days after exposure. Most colds last about a week, though a lingering cough or congestion can stretch to two weeks.

Spread: Easily transmitted through droplets from coughing/sneezing or touching contaminated surfaces, especially in crowded places like schools or offices.

Treatment: There is no cure for common colds. Manage with rest, fluids, and OTC remedies like decongestants, pain relievers (acetaminophen/ibuprofen), honey for cough (ages 1+), and saline nasal sprays. No antibiotics are needed since viruses cause colds.

Flu: Sudden and Intense

Influenza hits fast and hard. One day you’re fine, the next you’re in bed with chills and body aches.

Key symptoms:

• High fever
• Chills
• Muscle and joint pain
• Headache
• Sore throat
• Deep cough
• Extreme fatigue

COVID-19: Unpredictable and Varied

Caused by SARS-CoV-2, COVID-19 ranges widely in severity, ranging from no symptoms at all to severe illness.

Typical symptoms:

• Fever, chills, cough, sore throat
• Shortness of breath
• Loss of taste or smell
• Body aches, headache, fatigue
• Stomach upset: nausea, vomiting, or diarrhea

Onset and duration: Symptoms usually appear 2–5 days after exposure, but can take up to 14 days. Mild cases may resolve in 1–2 weeks, but fatigue or other effects can persist longer. Severe cases may require hospitalization.

Spread: Spreads mainly through the air in close indoor contact. Good ventilation and masks can reduce risk.

Treatment: Rest and hydration for mild cases; antiviral medications (such as Paxlovid) may be prescribed for higher-risk patients. Vaccination lowers the risk of severe illness.

When to See a Doctor: Know the Red Flags

Most people can manage allergies, colds, or mild flu and COVID at home with rest, fluids, and time. But sometimes, symptoms signal something more serious and waiting it out isn’t the best option.

When to Seek Immediate Medical Attention

• Trouble breathing — fast, wheezy, or labored
• Chest pain or tightness
• High fever — over 102°F, or one that won’t go down after a few days
• Sudden worsening — you start to feel better, then take a turn for the worse
• Signs of dehydration — dizziness, dry mouth, barely peeing
• Confusion or bluish lips/fingertips

Other Reasons to Contact Your Doctor

• You have a chronic condition like asthma, COPD, diabetes, or heart disease
• You’re pregnant
• You’re caring for someone vulnerable: a baby, older adult, or someone with a weakened immune system
• For infants under 3 months: any fever, poor feeding, or unusual sleepiness
• Severe ear pain, sinus pressure, or a sore throat that makes swallowing nearly impossible
• A persistent cough or wheeze that won’t let up

Why It Matters

• Flu and COVID-19 can lead to pneumonia or other complications
• Colds can trigger asthma attacks
• Allergies can block sinuses and lead to infection

Recognizing red flags early means you can get treatment before symptoms become dangerous.