Is there a homeopathic remedy which acts as an antihistamine?

Homeopathy. Homeopathic medicatios may have been appropriate for our ancestors however, "natural" does not mean "safe". A natural compound often contains hundreds of chemicals, many of which have not been studied. These "natural"complounds are not investigated by the fda for safety. Take a well studied medication that has been fda approved if you want defined safety and efficacy.
Not exactly but... Anithistamines block the action of histamine. I doubt homeopathic remedies work via this mechanism, but homeopathy can be very effective in treating allergies. As for safety, experts estimate 106,000 or more people in the US die each year due to "FDA-approved" pharmaceuticals, which cause significant side effects in millions of others. No homeopathic medicine has ever been shown to kill anyone!
Remedies can help. Homeopathic remedies are very safe. They are natural substances in ultradilution that have a resonating affect and stimulate the body to heal itself. They do not act like a drug as they work to stimulate the body to heal itself. Remedy selection is based on a good history to understand all the symptoms.
No. Truly homeopathic "medications" are made by repeated dilutions, so that the ingredient is not really there anymore (just the "essence" of it remains). That means there is no active ingredient left to cause any benefit. However, that also implies that the homeopathic "medicine" should be pretty harmless, unless some other non-homeopathic ingredient (such as some antihistamine chemical) was added.