How do I Tell the Difference Between Measles and Chickenpox?

Measles and chickenpox share some basic similarities, but they are caused by different viruses and have different symptom patterns. Both viruses cause rashes, but they don't usually look the same, and people tend to be sicker with measles than with chickenpox. Another difference is that people with measles often have a fever a degree or two higher than they might if they had chickenpox.

The virus that causes chickenpox is the varicella-zoster virus, while the other is simply called the measles virus. Both are highly contagious diseases that can spread through coughing, sneezing, and close contact with an infected person. Chickenpox can spread through contact with skin blisters, and measles through contact with nasal or throat secretions.

In people who have been vaccinated against these viruses, it’s relatively easy to tell the two diseases apart. A person who is vaccinated against measles is very unlikely to get the disease, but this is not the case with chickenpox. A person who has had the pox vaccine can still get the illness, but the symptoms are typically mild, with a light rash and quicker recovery.

Measles symptoms typically develop one to two weeks after contact with an infected person, while chickenpox symptoms begin to show after ten days to three weeks. During the first few days of illness, both diseases usually cause a fever, runny nose, and cough. Measles sufferers often have a sore throat and a rash of white spots inside the cheeks, while people with chickenpox tend to have a headache or stomach ache.

These early symptoms are almost always accompanied by an increase in body temperature. Two or three days after the first measles symptoms appear, the fever usually increases to between 104 and 105°F (40 to 40.56°C). People with chickenpox rarely have a fever this high; around 101 to 102°F (38.3 to 38.9°C) is typical.

A chickenpox rash usually starts to develop slightly before a person’s fever increases, while in the case of measles, the rash and fever tend to develop at around the same time. For both diseases, the rash develops over three to five days, and then lasts for approximately one week. After this time, it fades and the skin begins to heal.

The rashes sometimes appear similar in the beginning, but quickly develop some important differences. The main difference is that a person with chickenpox develops sores that fill with fluid and turn into blisters. These sores tend to appear in groups, but the blisters are usually separate, and don’t join up. In contrast, measles sores do not contain fluid, but are small, raised, red areas of skin. They also tend to join together to create large patches of rash. Another difference is that while pox blisters turn into open sores that crust over, measles rash does not, although the skin often becomes dry and flaky.

Measles and chickenpox rashes both tend to itch, but pox rashes are usually itchier. As a result, people with chickenpox are more likely to scratch their skin to the point where infection develops in one or more sores. This also means a greater likelihood of scarring as well.

Another way to distinguish between these illnesses is that a few days after the rash appears, many people with chickenpox feel much less sick. They might have mild stomach discomfort, feel irritable, or have trouble with itching, but fever and other viral symptoms usually decrease. People with measles are typically sicker for longer, with fever, fatigue and achiness, coughing, runny nose, and watery eyes. Both illnesses last for approximately ten days to two weeks, but those with the measles tend to be sicker for a longer portion of that time.

Being able to distinguish between measles and chickenpox is important for several reasons. One is that, while there is no antiviral treatment for measles, there are medications for chickenpox that can help the symptoms if given early enough. Apart from this difference, the treatments for the two illnesses are similar, with bed rest, hydration, good nutrition, and not scratching the skin being most important.

While aspirin and ibuprofen can both help relieve some symptoms of the illnesses, it can be dangerous for a person with chickenpox to take these medications. Aspirin can cause a complication called Reye's syndrome, in which symptoms such as confusion, nausea and vomiting, aggressiveness or irritability, and loss of consciousness can develop suddenly. These symptoms require emergency medical care. Ibuprofen is dangerous because it increases the risk of secondary infections, such as pneumonia.