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What is a Symptom?
July 30, 2026
Estimated Reading Time: 4m
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Whether in popular medical literature, waiting room brochures, coverage of disease outbreaks, or the media, the word symptom is often one of the first things you encounter. What are the symptoms of the flu, dengue fever, and COVID‑19?
But do we really know what a symptom is?
A good way to understand this is to compare it with what a sign means in the context of doctor‑patient communication.
The fundamental difference is this:
- A symptom is subjective and only perceived or experienced by the patient (for example, body aches, headache, nausea or fatigue).
- A sign is objective and can be observed, measured, or heard by another person, such as a doctor (for example, a rash, fever or high blood pressure).
However, a skin rash can be a sign, a symptom, or both.
A Concrete Example
- If the patient notices a skin rash, it is a symptom.
- If the doctor, nurse, or another healthcare provider also notices the rash, it is a sign.
- If both the patient and the doctor observe the rash, it may be considered both a sign and a symptom.
Regardless of who notices it first, signs and symptoms are the body's way of alerting the person or healthcare professional that something is wrong. Some signs and symptoms require follow‑up by a provider, while others may disappear completely without treatment.
Identifying the signs of a condition or disease has become increasingly dependent on the doctor as technology has advanced.
A Bit of History
When Antony van Leeuwenhoek, a merchant who had no formal science training but a keen interest in biology, invented the microscope and used it to discover cells and microbes in 1674, he opened the door to identifying signs of disease that were invisible to the naked eye.
These include foreign organisms in the blood and urine, changes in the composition of blood and waste products such as stool, as well as other important microscopic signs.
These indicators can make the difference between normal bodily function and serious diseases or conditions that affect it.
Three Types of Symptoms
Chronic Symptoms. These are symptoms that never go away or are recurrent, meaning they come and go. They are often seen in long‑term illnesses, such as diabetes, asthma or cancer.
Resolving Symptoms. These are symptoms that improve or disappear completely. For example, the symptoms of common indigestion may last for several days and then vanish without treatment.
Recurring Symptoms. These are symptoms that may disappear but later return. They are symptoms that appeared in the past, went away, and then reappeared. For example, the symptoms of depression may disappear for years, but then return.
Symptoms that Never Appear
The world of symptoms and signs is not linear; it can be elusive and go unnoticed for a long time. Some diseases do not present any symptoms at all. For example, a person may have high blood pressure for years without knowing it, and certain types of cancer do not show symptoms until they reach advanced and more aggressive stages.
These are known as asymptomatic diseases. Although we usually associate illness with pain, discomfort, or some obvious sign that something is wrong in the body, some diseases can develop without causing any symptoms and still become life threatening.
That is why routine preventive screenings are essential at the recommended age, or earlier if there is a family history of certain diseases.
Many infections can also progress without symptoms. These are known as subclinical infections, and even though the person does not show symptoms, they can still be contagious. In fact, the infectious agent can be transmitted during the incubation period, the time between infection and the appearance of the first symptoms.
Furthermore, subclinical infections can cause complications that extend beyond the infection itself. For example, an untreated urinary tract infection can increase the risk of premature birth.
In any case, it is important to pay attention to changes and schedule a visit with your primary care physician if your body is "talking to you" through a symptom you had not noticed before.
Sources
Cleveland Clinic, “Signs vs. Symptoms: Here’s Why They’re Different”
GoodRX, “Are Symptoms and Signs the Same?”
Journal of Clinical Practice and Research, “Confusing Terminology in COVID‑19: Signs, Symptoms, and Physical Findings”
JAMA, “Signs & Symptoms”
Medical News Today, “Why do signs and symptoms matter?”
Pivot Health Data Breach
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