Benadryl D

So my mother in laws boyfriend has been giving my 2 yr old niece benadryl D for a cold. Now I know that as long as the dosage is right, regular benadryl is ok. But everything I'm reading online says that the d part is a no no. He claims he asked the pharmacist but he is also known to be a huge liar and extremely selfish. Does anyone know anything about Benadryl D and tiny 2 yr olds?