Eating 25 kg of watermelon in 5 days means consuming about 5 kg per day. For a generally healthy adult man in the summer, this amount isn't considered excessive. However, the issue is that this man is diabetic, and watermelon is a high-glycemic-index food. In such cases, if blood sugar control is not carefully managed, blood sugar levels can rise, worsening the diabetes condition. This could lead to a temporary decline in immunity. Of course, not all the blame can be placed on his diabetes. If he was also staying up late, drinking alcohol, watching the Euros and the Olympics these past few days, that would further lower his immune defenses, potentially leading to shingles. After all, shingles is a viral skin infection that is prone to occur when immunity is low.

Therefore, for middle-aged and elderly people with underlying health conditions, especially those over 50 who have never had shingles, it is recommended to get the shingles vaccine if financially feasible. For example, the imported recombinant shingles vaccine has an efficacy rate of up to 97% in preventing shingles.

Of course, when herpes zoster occurs, it is recommended to take oral antiviral drugs within 72 hours, including but not limited to acyclovir, famciclovir, valacyclovir, or brivudine; oral nerve-nourishing medications such as Vitamin B1 and mecobalamin; oral pain-relieving drugs like gabapentin, pregabalin, or ibuprofen; and topical antiviral agents such as acyclovir cream or penciclovir cream. If secondary infection occurs, topical mupirocin or fusidic acid cream can be applied. Red light physical therapy can also be used in combination.

Despite such aggressive treatment, some individuals over the age of 60 may still experience postherpetic neuralgia, and for some, the pain can be quite severe and persistent, significantly impacting their quality of life. At this stage, dermatologists are often at a loss and must seek comprehensive treatment involving multiple disciplines such as pain management, traditional Chinese medicine, and psychology. This type of neuralgia truly leaves many people in agony.

Therefore, individuals with underlying conditions must, under the guidance of a physician, control and improve their health through proactive medication and lifestyle interventions. This includes engaging in appropriate physical exercise, avoiding prolonged periods of staying up late, maintaining a relaxed mindset, ensuring a balanced diet, and receiving necessary vaccinations to prevent subsequent diseases, such as herpes zoster.