You Do Need power plug adapter while traveling from Switzerland to Eritrea.

Here is Why You Need An Adapter

The outlet and plug type used in Eritrea are C and L and in Switzerland are C and J. This is how they look like.

Switzerland

In Switzerland, outlets of type C and J are in use.

Type C

Type J

Eritrea

In Eritrea, outlets of type C and L are in use.

Type C

Type L