Nested header files are achievable in C, allowing the inclusion of one header file within another. However, while this is permitted, it can lead to confusion and increased compile times, so it's advisable to minimize their use. To prevent issues with a header being included multiple times in a source file from different paths, it's essential to implement include guards. This can be done using the standard preprocessor directives #ifndef, #define, and #endif, or by using the #pragma once directive if supported by the compiler.