Sniffles in the summer usually signal allergies, but if you catch a summer cold, be warned: it can be much nastier than the winter variety.

As the Wall Street Journal reports, colds during the summer can last for weeks, while their winter counterparts may only stick around for a few days. But why are summer colds harder to get rid of?

1. They're caused by different viruses than winter colds.

The enterovirus, which is reportedly responsible for most summer colds, takes longer to eradicate and can recur after the initial infection. In addition to being contracted through contact with germ-infested surfaces, it can also be spread through fecal-oral contact, for example, bathroom door handles, notes the Wall Street Journal. This is why hand-washing is especially important for preventing a summer cold.

According to the National Institutes of Health, enteroviruses cause about 10 million to 15 million illnesses annually across the country, usually between June and October.

Since it takes so much longer to leave your body, you might mistake a summer cold for allergies. But there's an easy way to make the distinction between the two: mucus. Is it green? Then, you have allergies. Clear? You've probably got a summer cold, Dr. Weber, a professor at the University of Colorado at Denver, told the Wall Street Journal. He adds that itchy eyes, nose, and ears all point to allergies, too.

In addition to respiratory issues associated with winter colds, a summer cold is accompanied by diarrhea, rashes, and nausea, notes the NIH.

2. Your summer exercise routine is not doing you any favors.

When a cold hits, you might be inclined to "sweat it out," but this tactic could backfire for a cold during the summertime. Roger Baxter, co-director of the Kaiser Permanente Vaccine Study Center told WSJ why this could actually prolong your illness:

"'The body tries to use all its metabolic resources to fight off disease, so a hard run or long gym session diverts some of that energy away from fighting the sickness,' he says. Although consistent, moderate exercise tends to protect the body from illness, a sudden and strenuous workout can decrease the body's immunity."

What can you do to prevent getting a summer cold?

Since viruses travel through direct contact with saliva, mucus, or in the fecal matter of an infected person, frequent hand washing is a must in preventing the spread of infection, according to Dr. Michael Pichichero, a pediatrician and infectious disease researcher at the Rochester General Hospital Research Institute told the NIH. He adds, "it’s all about blocking viral transmission.”

Besides hand-washing, try to avoid extreme temperature differences, such as moving from the frigid tundra of your office into the blazing heat of the outdoors. Ronald Eccles, director of the Common Cold Centre at the University of Cardiff in Wales, told WSJ that the chilling "lowers the defenses in the nose and throat by causing constriction of the blood vessels." He added, "If a virus is already present, this reduces our immunity."

[h/t Wall Street Journal]