Sunscreen and mosquito repellent for a 4-month-old baby?

Hello, thank you for your question! The skin of babies under 6 months is extremely sensitive and your best prevention is shade under the parasol, hat, and long sleeves. Don't forget the sunglasses, because the sun hits twice, by reflecting on the sand. If sun exposure cannot be avoided for a short time, you can apply a 'physical' screen on the skin, such as zinc oxide (Zincofax for example)

For children under 6 months of age, physical nets (bedroom, around the bed) are mostly recommended. Canadian health authorities do not recommend the use of insect repellent under 6 months of age, but the US Environmental Protection Agency mentions that small concentrations of DEET are safe (10%)

Hope this helps, don't hesitate if you have any other questions!