Compare symptoms of common illnesses Seasonal allergies Influenza (the flu) Norovirus (stomach flu) Frequently asked questions When you’re feeling sick, it can be confusing to tell what’s causing your symptoms, especially since many common illnesses share similar signs. Symptoms like a stuffy nose, cough, or fever can point to multiple common illnesses, so it’s important to pay attention to how you feel and how severe your symptoms are. Knowing these details can help you figure out if and when you should talk to a doctor to get help. This symptom checker helps you compare common illnesses, including seasonal allergies, colds, flu, COVID-19, RSV, and norovirus to better understand how symptoms and timing differ and when it may be helpful to talk to a doctor . Begin with the chart below to compare common symptoms and learn what illness may be affecting you. Seasonal allergies Seasonal allergies or hay fever, formally known as allergic rhinitis, happen when your immune system reacts to allergens like pollen in the air. This reaction causes symptoms such as sneezing, itchy eyes, and a runny nose. Pollen levels tend to be highest during warmer months, typically from early spring through late fall. Different plants release pollen at different times of year, including: Trees such as birch, oak, elm, and maple in the spring Grasses in late spring and summer Ragweed in the fall Seasonal allergies are very common, affecting an estimated 40 to 60 million people in the United States each year. Seasonal allergy symptoms are typically mild to moderate, though they can be more severe and debilitating for some individuals. Mild to moderate symptoms that appear as a reaction to allergens may include: Itchy nose, mouth, eyes, throat, skin, or any area Problems with smell Seasonal allergies may also lead to more symptoms that onset later such as: Stuffy nose (nasal congestion) Clogged ears and decreased sense of smell Dark circles under the eyes Puffiness under the eyes Fatigue and irritability If your symptoms are making it hard to go about your day, or if you're not sure whether what you're feeling is caused by allergies or something else, talk to a healthcare provider . They can help figure out what's going on and recommend ways to help you feel better. Due to the nature of how people are affected by seasonal allergies, the duration of symptoms can typically range from a few weeks to several months, depending on location, personal allergy triggers, and immune health. If you are experiencing: Severe or debilitating allergic symptoms Treatment that used to work but no longer does Symptoms not responding to treatment Talk to a doctor — there are over-the-counter (OTC) and prescription medications that may help relieve symptoms of seasonal allergies for many people. A cold is a respiratory illness caused by different types of viruses. Rhinovirus is one of the most common causes, responsible for up to 50% of colds. Colds frequently circulate in winter and spring, but you can catch a cold at any time of the year. Cold symptoms can be similar to flu symptoms, but they’re generally milder, and usually include the following: Runny or stuffy nose Low-grade fever (typically in children or older adults) Cold symptoms typically peak within 2-3 day of infection, and most people will recover from a cold within a week. Some symptoms, such as runny or stuffy nose or a lingering cough, may last up to two weeks but should gradually improve. If you experience any of the following, you may want to consider calling a healthcare professional: A fever lasting longer than four days, or, in babies younger than three months, a fever that is 100.4 °F (38 °C) or higher Symptoms that last 10 days or more with no improvement Fever, cough, or other symptoms that improve but then return or become more severe Difficulty breathing or rapid breathing Chronic health conditions that worsen Any other symptoms that are severe or cause you concern Influenza (the flu) The flu, also known as influenza, is a respiratory illness caused by different influenza viruses. The flu can range from mild to severe. Certain groups of people, including young children, pregnant women, older adults, and people with underlying health conditions, may be at risk for serious complications, hospitalization, or, rarely, death. An annual flu vaccine can help reduce your risk of getting the flu and experiencing serious complications. The Centers for Disease Control and Prevention (CDC) recommends, with few exceptions, that everyone six months and older get a flu vaccine at the start of every flu season, ideally in September or October. To check vaccine eligibility and book vaccination appointments, visit VaxAssist by Pfizer . Like any vaccine, the flu vaccine may cause side effects, such as soreness at the injection site, low-grade fever, or body aches. These are usually mild and go away on their own within a day or two. It's also important to know that the flu vaccine's effectiveness can vary from season to season, depending on how well the vaccine matches the viruses that are spreading. Even so, getting vaccinated can help reduce the severity of illness if you do get sick. Talk to a doctor or pharmacist about whether the flu vaccine is right for you. Flu symptoms can be similar to cold symptoms, but they’re generally more severe; they can also be similar to COVID-19 symptoms. Common flu symptoms include: Runny or stuffy nose Muscle or body aches Vomiting or diarrhea (more common in children) Most people with the flu will recover in a few days, while others may take closer to two weeks to recover. If complications arise, recovery could take longer and require medical assistance. There are many flu symptoms that demand medical attention, and some people develop complications (such as pneumonia) that can be life-threatening and result in death. The following list includes several of them, but it’s not exhaustive. Always call your doctor if you’re concerned about a symptom such as: Fast breathing or trouble breathing Chest pain or pressure Severe muscle pain Dehydration or not urinating Not alert or not interacting normally when awake; confused; dizzy Severe weakness Fever or cough that improves but then return or worsens Chronic medical conditions that worsen COVID-19 is a respiratory illness caused by the virus SARS-CoV-2, a type of coronavirus. COVID-19 can impact people in different ways, with some people experiencing symptoms similar to the flu. COVID-19 can be asymptomatic or have symptoms ranging from mild to severe. Older adults and people with underlying health conditions may be at greater risk of developing serious complications. If you think you may have been exposed to COVID-19 or are starting to feel sick, it's a good idea to talk to a healthcare provider early, especially if you are at higher risk for severe illness. Early conversations with a doctor can help you understand your options, including whether testing or treatment may be right for you. The CDC recommends a COVID-19 vaccine for certain people based on individual-based decision-making, also known as shared clinical decision making. Check your eligibility and book vaccination appointments at VaxAssist by Pfizer . As with other vaccines, COVID-19 vaccines may cause side effects. Common side effects can include soreness at the injection site, tiredness, headache, muscle aches, or low-grade fever. These are usually mild and tend to go away within a few days. How well the vaccine works may also change over time as the virus evolves, which is why updated vaccines are made available. Talk to a healthcare provider about the benefits and risks, and whether staying up to date on COVID-19 vaccination makes sense for you. Could acting early make a difference with COVID-19? See whether early action may help lower risk for progressing to severe COVID-19. Medical understanding of COVID-19 continues to evolve. The following list includes a number of commonly reported symptoms, but symptoms can vary from person to person. Talk to a healthcare provider if you think you might have COVID-19. Fever or chills Shortness of breath or difficulty breathing Muscle or body aches New loss of taste or smell Runny or stuffy nose Nausea, vomiting, and diarrhea If you test positive for COVID-19, understand that many mild cases tend to begin improving after one to three weeks, though recovery for some people may take longer. Others may experience long-term symptoms, including symptoms that last 3 or more months, known as Long COVID . COVID-19 can lead to serious complications and even death. Call for help immediately if you are experiencing any of the following symptoms: Difficulty breathing Ongoing pain or pressure in the chest

A sense of confusion Trouble staying awake or waking up Blue, gray or pale tint to the skin, lips or nail beds If you believe you may be at higher risk for severe COVID‑19, you may benefit from taking the risk assessment and talking to a doctor promptly if symptoms develop. To learn more about COVID-19, visit the COVID-19 Overview . Patients with severe COVID-19 had a 2x higher risk of developing Long COVID symptoms RSV, short for respiratory syncytial virus, is a highly contagious respiratory virus that usually causes mild, cold-like symptoms. It can infect the nose, throat, and lungs, and symptoms typically appear four to six days after getting infected. Most people recover within one to two weeks, but RSV can sometimes lead to more serious illnesses, such as bronchiolitis or pneumonia, especially in people at higher risk. While RSV can affect anyone, the CDC recommends RSV vaccination for: Adults ages 75 and older Adults ages 50 to 74 with certain underlying medical conditions that increase their risk of severe illness Pregnant women if 32 to 36 weeks gestation falls between September and January to help protect newborns for the first six months (in most of the US depending on RSV seasonality) RSV vaccination can help reduce the risk of severe illness and hospitalization in eligible adults. For infants, other types of immunization (such as monoclonal antibody products) may be available to help protect against severe RSV. Talk to your child's pediatrician about the best option. As with any vaccine or immunization, RSV prevention options may cause side effects. In adults, common side effects of RSV vaccination can include pain at the injection site, tiredness, headache, or muscle aches. For infants receiving preventive immunization, side effects may include pain or redness at the injection site. Side effects are generally mild and tend to go away on their own. Talk to a healthcare provider about the benefits and risks to find out which prevention option, if any, is right for you or your child. RSV symptoms typically mimic cold symptoms and can appear within 4 to 6 days of being exposed to the virus. Symptoms of RSV typically appear in stages, and can include: Decrease in appetite Most RSV symptoms last around one to two weeks. While many people start to feel better within this time, some may continue to notice symptoms such as lingering cough, wheezing, or tiredness even after other symptoms improve. Most RSV infections improve on their own, but RSV can become more serious in some people. Talk to a doctor if you or your child has RSV symptoms and you notice any of the following: Difficulty breathing Not drinking enough fluids or signs of dehydration Symptoms that are worsening (instead of gradually improving) Norovirus (stomach flu) Norovirus is sometimes referred to as a ‘stomach bug’ or ‘stomach flu’ though it is not related to influenza (the flu) which is caused by the influenza virus. Norovirus is a virus that can spread through contaminated foods and water or contact with an infected person. It is one of the leading causes of acute gastroenteritis, which is a temporary, rapid-onset inflammation of the stomach and intestines that can result in diarrhea, vomiting, nausea, and abdominal cramps, and is the top cause of foodborne illness. Norovirus can strike at any time of year but is most common from November to April. Most people with norovirus start to feel better within a few days, but it can lead to dehydration, especially in young children, older adults, and people with other health conditions. If symptoms feel severe or you're having trouble keeping fluids down, talk to a healthcare provider . If you think you may have stomach flu or a stomach bug, it could be norovirus. Common symptoms include: Less common symptoms include: A person usually develops symptoms 12 to 48 hours after being exposed to norovirus. Generally, people with norovirus recover in one to three days. You should talk to a doctor if you have any of the following: Dehydration symptoms Severe dehydration Diarrhea that continues after two days Understand the symptoms, know when to get help When symptoms overlap, understanding how illnesses differ and knowing your personal risk can help guide next steps. Comparing symptoms and onset patterns can clarify when monitoring may be appropriate and when care should not be delayed, especially for people at higher risk of severe illness. If symptoms feel severe, last longer than expected, or raise concern, talking with a doctor can help determine whether testing, treatment, or additional care may be needed. Frequently asked questions Can I be sick without a fever? Yes, you can be sick without having a fever. A fever is just one possible sign of illness, but many common problems like colds, allergies, or sinus infections can make you feel sick without raising your temperature. Pay attention to your symptoms and how you feel overall, and if your symptoms feel severe, even if you don’t have a fever, talk to a doctor . Why am I always sick? Feeling sick often can happen for a few common reasons. Stress, poor sleep, not eating well, or being around a lot of germs are some of the reasons that can make it harder for your body to stay healthy. Having health problems like allergies or asthma, or having an undiagnosed chronic illness may make you feel sick more often. If you seem to get sick all the time, or an illness is not getting better, talk with a healthcare provider and share your concerns. Why do some symptoms come and go? Symptoms can come and go because your body is reacting to changes as it heals or responds to triggers. Things like activity level, stress, sleep, allergies, or how well-rested you are can make symptoms better or worse at different times. Many illnesses do not improve in a straight line, so it is common to feel better one day and worse the next. How do I know if I’m getting sick? If you notice signs like fatigue, scratchy throat, body aches, headache, or mild congestion, these symptoms could be early signs of a worsening illness. Resting early and staying hydrated can sometimes help keep symptoms from getting worse. What are “red flag” symptoms? 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