Summer offers a wide variety of fruits, but eating too much of some can lead to symptoms like toothaches, red and swollen eyes, inflammation at the corners of the mouth, nosebleeds, constipation, and coughing. This is what's known in Traditional Chinese Medicine as "internal heat" or "上火" . Here's a list of summer fruits that are likely to cause internal heat, so you shouldn't eat them without restraint!
Lychee
There's a common saying, "One lychee is equivalent to three fires of internal heat." Although lychees are refreshing, they are actually considered a "heaty" fruit.
The famous line from a classical poem, "I'd happily eat three hundred lychees a day and never regret being a southerner," should not be taken literally. Generally speaking, freshly picked lychees are slightly better. The longer lychees are stored, the higher their sugar content and the more "heaty" they become, making it easy to develop internal heat from eating too many.
However, when eaten in moderation, lychees are very nutritious. For women, lychees can also help prevent freckles and promote smoother skin.
Durian
Many people know that eating too much durian can cause internal heat, and there is some scientific basis for this. Durian is rich in nutrients but also very high in calories, especially in sugar. Thailand's Ministry of Public Health advises the public not to consume more than two segments of durian in a day. If you eat too much at once, the excessive nutrients can overload your digestive system, which may not be able to fully absorb sugars and other nutrients, potentially leading to symptoms like canker sores. People who are obese, have high blood pressure, or are diabetic should especially avoid eating too much. Additionally, durian is high in potassium, so those with kidney disease should consume it with caution.
Orange
The idea that "eating oranges causes internal heat" mainly comes from how convenient they are to eat. It's easy to unknowingly consume many in just a few minutes while sitting around. Especially very sweet oranges tend to have a high sugar content. For people with poor sugar absorption, a high concentration of sugar from eating too many can cause fluid to be drawn out of throat cells, leading to throat discomfort. Furthermore, bacteria in the mouth thrive in high-sugar environments. If you don't rinse your mouth after eating oranges, this can easily lead to gum inflammation, making you feel like you have "internal heat."
Rambutan
Rambutan, similar in taste to lychee but much larger, is now a common fruit at stalls despite its tropical origins. Many people love the sweet and sour taste of rambutan, and a few juicy ones can be especially thirst-quenching and appetizing in the dry winter. However, a reminder: rambutan is a "warm-heat" fruit, and eating too much can easily cause internal heat.
Those suffering from "heat-related" ailments such as mouth sores, dry mouth and throat, tonsillitis, acne, bad breath, constipation, hemorrhoids, or a cough with yellow, thick phlegm should not eat too many rambutans.
On the other hand, people with a "cold" body constitution, such as those who are sensitive to cold, cannot drink cold water or other cold beverages, or suffer from menstrual pain, can适量 consume rambutan.
Peach
Eating too many raw peaches can cause bloating and sores, and is more harmful than beneficial. Because peaches are a "heaty" fruit, eating too many can easily lead to internal heat, and in severe cases, can even cause sores to appear on the body. This is especially true for people who already have "internal fire." Although peaches can help relieve constipation, for those whose constipation is caused by internal heat, eating a lot of peaches will not only fail to relieve it but may make it worse. People bothered by symptoms of internal heat such as a dry mouth, thirst, or a sore throat should also eat fewer or no peaches.