I've noticed that several kyaraben/charaben (cute bento) oriented Japanese bento blogs are scaling back on the intricacy of their bentos recently. It gets very warm and humid in the summer throughout most of Japan, so food safety is a big issue. Complicated charaben require a lot of handling of the food, which should be avoided when the weather is warm.

I have already put together a comprehensive list of bento safety tips, but here are some top summer bento safety tips.

• Heat through cooked food, and then cool it down before packing into a bento box. This is a fundamental rule of bento safety.
• Use a cooling element whenever you can. This can be an ice pack like the one in the photo, or portions of your bento pre-frozen (examples here, here, here, and here. A small ice pack is a very handy thing to have: if you're buying just one, choose a soft-gel in a bag model, which is lighter than the kind in rigid plastic containers. (I put my bento box and ice pack into an insulated six-pack cooler that I got as a promotional giveaway many years ago, padded with a towel that doubles as a handwipe.)
• Don't handle food too much. Ease up on the intricate bento decorations unless you are very fast and good, until it gets cooler.
• Cook proteins through thoroughly. No raw fish or half-cooked meat, or moist tofu! Fried tofu or tofu cooked through thoroughly (e.g. scrambled tofu) is ok because much of the moisture has been cooked off, but plain blocks of tofu should be avoided. Remember that bacteria love moisture!
• Keep your hands, utensils and bento boxes clean. Beware of cross contamination, such as touching raw food (e.g. vegetables) with a spatula you used to cook meat. And of course, wash your hands before handling any food!
• Be careful of uncooked food as well as cooked. I think there is a tendency to be overly cautious of cooked food safety while forgetting that raw food, such as salads, can be just as prone to contamination. If you're carrying salads and raw vegetables for lunch, I highly recommend using an ice pack.