Eating watermelon when you have a cold, you can replenish some of the water and vitamins, and overall it will not have much effect on the course of the cold. But generally speaking, this little bit of water and vitamins will not play a significant role in shortening the duration of the cold, so as long as you are willing to eat, you can eat a small amount, just do not eat a lot. When you have a cold, the diet is mainly light, cold food, such as watermelon, and if you eat too much, it may cause symptoms in the spleen and stomach of some people, such as causing diarrhea. So watermelon can be eaten, but it is not advisable to eat too much. If these people have normal spleen and stomach function, eating some watermelon in moderation will generally not lead to diarrhea and other discomfort.