A Doctor's Guide to Fall Sickness: Cold, Allergies, or COVID?

Dr. Myriam Delgado, MD
Sep 18
7 min read

A physician's framework to help distinguish between fall allergies, the common cold, COVID-19, and the flu, guiding readers on when to test and seek medical care.

Dr. Myriam Delgado provides a clear, compassionate guide and a helpful chart to differentiate the overlapping symptoms of fall allergies, the common cold, COVID-19, and the flu, helping readers make informed decisions about testing and care.

Takeaways

Itchiness (eyes, nose) is a hallmark sign of allergies, rarely present in viral infections.
The common cold typically develops gradually, while the flu often comes on suddenly with intense body aches.
COVID-19 has the most variable symptoms, making testing the only way to confirm a diagnosis.
A high fever is common with the flu and COVID-19 but rare with a cold or allergies.
When in doubt, especially if you have been exposed or have a fever, test for COVID-19 to protect others.

Hello, I'm Dr. Myriam Delgado. As the leaves begin to turn and the air grows cooler, a familiar uncertainty settles in alongside the beauty of the season. A tickle in the throat, a sudden sneeze, an unexpected wave of fatigue—these are the small signs that can set off a cascade of questions. In my clinic, this is a conversation I have daily. A patient, let's call her Elena, called me just yesterday, worried about her young son. "He has a runny nose and a cough," she said, her voice filled with concern. "I don't know whether to send him to school, get him a COVID test, or just give him some rest. How can I possibly know what this is?"

Elena’s question is one we are all asking. The fall brings a convergence of ailments with remarkably similar symptoms. The high pollen counts from ragweed trigger allergies just as common cold viruses begin to circulate more freely in our schools and workplaces. All of this happens as we continue to coexist with COVID-19 and prepare for the flu season.

My goal here is to provide a clear framework to help you think through this puzzle. This guide is not a substitute for a diagnosis from a healthcare professional, but it can help you make sense of your symptoms, reduce anxiety, and take the right, proactive steps for your health and the health of those around you.

The Great Overlap: Why Are They So Similar?

First, it is helpful to understand why these conditions feel so alike. Your body’s immune system is a brilliant but busy security force. When it detects an intruder—whether it’s a harmless pollen grain or a threatening virus—it sounds an alarm. This alarm triggers a standard set of responses: inflammation (leading to a sore throat), increased mucus production (a runny or stuffy nose), and nerve irritation (sneezing and coughing).

Think of your symptoms as a single fire alarm bell. The bell rings the same way whether the fire is a small wastebasket fire (a cold), a faulty sensor (allergies), or a more serious kitchen fire (the flu or COVID-19). Our job is to look for the other clues to figure out what started the fire.

Profiling the Culprits: The "Personality" of Each Ailment

Each of these conditions has a typical pattern or "personality." By looking at the collection of symptoms, their timing, and their unique characteristics, we can often find a likely culprit.

Seasonal Allergies (The Predictable Intruder): The defining characteristic of allergies is the itch. Itchy eyes, an itchy nose, an itchy throat, even itchy ear canals. The mucus from allergies is typically thin, clear, and watery. Symptoms can last for weeks or even months—as long as the allergen (like ragweed) is present in the air. You will not have a fever or body aches with allergies.
The Common Cold (The Gradual Nuisance): A cold usually comes on slowly. It might start with a day of feeling "off" or a mild sore throat. Then, the nasal symptoms take over, often starting with a runny nose that later becomes thicker and more congested. A low-grade fever is possible, especially in children, but a high fever is rare in adults. You typically feel sick for a few days to a week and then gradually improve.
COVID-19 (The Unpredictable Chameleon): This is the master of disguise. COVID-19 has the widest range of symptoms of all. It can feel exactly like a mild cold, or it can present with more severe, flu-like symptoms. While the tell-tale loss of taste or smell from earlier variants is less common now, it remains a very specific clue if it appears. Key indicators that suggest something more than a cold include fever, body aches, a deep sense of fatigue, and sometimes gastrointestinal issues like diarrhea. Because its presentation is so variable, testing is the only way to be certain.
Influenza - The Flu (The Abrupt Assailant): The flu's personality is sudden and intense. People often say it feels like being "hit by a truck." One minute you feel fine, and the next you are laid low with a high fever, significant body aches, chills, and a headache. The respiratory symptoms might even be secondary to the overwhelming feeling of whole-body sickness.

The Symptom Sorter: A Doctor's Comparison Chart

To help you visualize the differences, here is a chart that organizes the most common symptoms. Remember, this is a general guide, and individual experiences can vary.

Symptom	Allergies	Common Cold	COVID-19	Influenza (Flu)
Itchiness (Eyes, Nose)	Key Sign	Rare	Rare	Rare
Fever	Never	Rare (low-grade)	Common	Common (often high)
Fatigue	Sometimes (mild)	Mild	Common (can be severe)	Key Sign (severe)
Cough	Sometimes (mild)	Common	Common (often dry)	Common (often dry)
Aches & Pains	Never	Mild	Common	Key Sign (severe)
Runny/Stuffy Nose	Common	Key Sign	Common	Common
Sore Throat	Sometimes (scratchy)	Common	Common	Common
Sneezing	Common	Common	Sometimes	Sometimes
Loss of Taste/Smell	Rare	Rare	Possible	Rare
Onset of Symptoms	Varies with exposure	Gradual (slow)	Varies	Sudden (abrupt)

The Most Important Step: When to Test and When to Talk to Your Doctor

This information is a guide to help you think, not a tool for self-diagnosis. After you've considered your symptoms, the next steps are practical.

When in doubt, test for COVID-19. At-home rapid tests are a valuable tool. If you have a fever, body aches, a new cough, or have been knowingly exposed to someone with COVID-19, testing is a responsible action. A positive test allows you to take steps to avoid spreading the virus to vulnerable people.
Contact your doctor or seek medical care if you experience any of the following:
- Difficulty breathing or shortness of breath.
- A high fever that doesn't respond to fever-reducing medication.
- Chest pain or pressure.
- Confusion or severe dizziness.
- Symptoms that are not improving after a week or are getting worse.

Summary: A Framework for Clarity and Calm

Navigating illness in the fall can be confusing, as the symptoms of allergies, the common cold, COVID-19, and the flu frequently overlap. By observing the distinct "personality" of each condition—the itchiness of allergies, the gradual onset of a cold, the sudden intensity of the flu, and the variability of COVID-19—you can gain a better sense of the likely cause. The provided symptom chart can serve as a helpful reference. Ultimately, this framework is designed to guide your actions, leading you to test when appropriate and to seek professional medical advice for any serious symptoms, helping you care for yourself and your community.

Final Thought

It is entirely normal to feel a sense of anxiety when you or a loved one falls ill. This uncertainty is a real and valid concern. My hope is that by arming yourself with this knowledge, you can replace some of that anxiety with a sense of calm and a clear plan of action. Listening to your body, observing your symptoms thoughtfully, and reaching out for help when you need it are the cornerstones of good health, not just in the fall, but all year round.

Frequently Asked Questions

Is it possible to have allergies and a cold or COVID at the same time?
Yes, it is definitely possible to have both. You might have your typical allergy symptoms (like itchy eyes) but then develop a fever and body aches. This is a situation where testing for COVID-19 or the flu would be very important to get a clear picture.
My only symptom is a sore throat. What could it be?
A sore throat is an early symptom of many viral infections, including colds and COVID-19. It can also be caused by allergies (from postnasal drip) or even just dry air. If the sore throat is your only symptom, it's best to monitor for other signs, rest, and stay hydrated. If it persists or you develop other symptoms, consider testing.
How long am I contagious if I have a cold or COVID-19?
For a common cold, you are generally contagious for a few days before your symptoms start and for up to a week after. For COVID-19, CDC guidelines often suggest you are most infectious in the first five days of illness, but you can continue to be contagious for longer. Following current public health guidance on isolation is the best practice.
Why do my allergies get so bad in the fall?
The primary culprit for fall allergies is ragweed pollen. A single ragweed plant can produce up to a billion pollen grains that can travel for hundreds of miles on the wind. Mold spores from damp fallen leaves are another common trigger.
When should my child stay home from school?
Generally, children should stay home from school if they have a fever, are vomiting, have diarrhea, or are not well enough to participate in regular school activities. With the prevalence of COVID-19, it is also wise to keep them home and test if they have new respiratory symptoms, per your school's guidelines.
Image Suggestion 2: A split-panel image. Top panel: A person looking miserable, surrounded by swirling pollen icons. Middle panel: A person in bed with a thermometer and tissues. Bottom panel: A person taking an at-home COVID-19 test. Caption: "Different causes, similar symptoms. Knowing the clues can help guide your next steps."
Image Suggestion 3: A calm, reassuring photo of a doctor talking to a patient via telehealth on a laptop screen. Caption: "When you are unsure or your symptoms are severe, a healthcare professional can provide a clear diagnosis and treatment plan."

References

Centers for Disease Control and Prevention (CDC). (2024). Cold Versus Flu.
Centers for Disease Control and Prevention (CDC). (2024). Symptoms of COVID-19.
American College of Allergy, Asthma & Immunology (ACAAI). (n.d.). Allergies or Cold.
Mayo Clinic. (2023). Cold, flu or allergies?.

About Dr. Myriam Delgado

Dr. Myriam Delgado is a compassionate physician with Biolife Health Center. She is dedicated to helping individuals understand and manage their health challenges. Dr. Myriam Delgado is committed to empowering her patients to live their best lives by providing supportive and practical guidance. Her work focuses on clinical studies and putting complex health findings into plain language so that people can make informed decisions.