Hamilton told MLB.com that he's sick with sinus congestion that makes him prone to dizziness and sensitive to the lights at major league stadiums.
"I'm just off," Hamilton said. "However you want to write it, however you want to describe it -- I'm just off."
Hamilton, pulled from Monday's game after six innings, said the condition has been an issue during his career. Hamilton said the latest bout began May 5, but insisted his body still feels "great."
"It was good in Houston and it felt OK in Chicago. Today it felt better," Hamilton said after the game. "I felt like I was seeing the ball better and had a little better pitch selection throughout the game. I felt OK while I was hitting. But like last night, once I would run, I'd kind of feel a little off. So we'll give the medicine a couple of days and see if it kind of works its way out."
Hamilton said he is trying to find an antibiotic to "put a Band-Aid on it," and he insisted the ailment won't keep him out of the lineup.
"I've felt bad plenty of times and played and done well," Hamilton said. "This has nothing to do with that. It's more of, I'd say probably being out-on-the-field type of thing -- run the bases, then go out on the field, combined with lights and all that stuff. It's not the best thing at this moment."
The first-year Angels' slugger, who signed a five-year, $125 million deal in December, said he will see an allergist to find a permanent solution.
According to Hamilton, this latest ailment is unrelated to the vision condition "ocular keratitis," which Hamilton battled last season. Hamilton said that issue was linked to caffeine consumption.
Information from The Associated Press was used in this report.