What Do Itchy Rashes On The Back, Legs And Arms Indicate?

My brother, 68, is on blood pressure meds and statins and our paternal grandfather died from multiple strokes. That said, since late fall he s been having itchy skin in patches on his back, legs and arms - not all at the same time. In the past 3-4 days, he s been experiencing pressure in the back of his head that doesn t last long, but has been recurrent. He says it happens after he stands or changes positions. He has been bicycling approximately 150 miles a week in Florida since Jan 1st. He may still be very slightly overweight. The headaches are concerning for him and he calls me for advice, since I am a Medical Technologist. I ve told him to log his headache occurences and what he is doing when they occur. Do you have any thoughts as to what might be causing the headaches? I can t find anything specific in the symptom checker. Thanks.