Memes

Antihistamine is the type of drug, or it’s “family. It describes what is does biochemically. That’s like using “antibiotic” when you are looking for doxycycline.

Antihystamine is very specific. Antihistamine is quite generic and it depends on whether you want to treat allergies or schizophrenia. Here is a list from Wikipedia of the most common type of antihistamines (targeting the H¹ receptor)

List of H1 antagonists/inverse agonists

Acrivastine
Alimemazine (a phenothiazine used as antipruritic, antiemetic and sedative)
Amitriptyline (tricyclic antidepressant)
Amoxapine (tricyclic antidepressant)
Aripiprazole (atypical antipsychotic, trade name: Abilify)
Azelastine
Bilastine
Bromodiphenhydramine (Bromazine)
Brompheniramine
Buclizine
Carbinoxamine
Cetirizine (Zyrtec)
Chlophedianol (Clofedanol)
Chlorodiphenhydramine[12]
Chlorpheniramine
Chlorpromazine (low-potency typical antipsychotic, also used as an antiemetic)
Chlorprothixene (low-potency typical antipsychotic, trade name: Truxal)
Chloropyramine (first generation antihistamine marketed in Eastern Europe)
Cinnarizine (also used for motion sickness and vertigo)
Clemastine
Clomipramine (tricyclic antidepressant)
Clozapine (atypical antipsychotic; trade name: Clozaril)
Cyclizine
Cyproheptadine
Desloratadine
Dexbrompheniramine
Dexchlorpheniramine
Dimenhydrinate (used as an antiemetic and for motion sickness)
Dimetindene
Diphenhydramine (Benadryl)
Dosulepin (tricyclic antidepressant)
Doxepin (tricyclic antidepressant)
Doxylamine (most commonly used as an over-the-counter sedative)
Ebastine
Embramine
Fexofenadine (Allegra/Telfast)
Fluoxetine
Hydroxyzine (also used as an anxiolytic and for motion sickness; trade names: Atarax, Vistaril)
Imipramine (tricyclic antidepressant)
Ketotifen
Levocabastine (Livostin/Livocab)
Levocetirizine (Xyzal)
Levomepromazine (low-potency typical antipsychotic)
Loratadine (Claritin)
Maprotiline (tetracyclic antidepressant)
Meclizine (most commonly used as an antiemetic)
Mianserin (tetracyclic antidepressant)
Mirtazapine (tetracyclic antidepressant, also has antiemetic and appetite-stimulating effects; trade name: Remeron)
Olanzapine (atypical antipsychotic; trade name: Zyprexa)
Olopatadine (used locally)
Orphenadrine (a close relative of diphenhydramine used mainly as a skeletal muscle relaxant and anti-Parkinsons agent)
Periciazine (low-potency typical antipsychotic)
Phenindamine
Pheniramine
Phenyltoloxamine
Promethazine (Phenergan)
Pyrilamine (crosses the blood–brain barrier; produces drowsiness)
Quetiapine (atypical antipsychotic; trade name: Seroquel)
Rupatadine (Alergoliber)
Setastine (Loderix)
Setiptiline (or teciptiline, a tetracyclic antidepressant, trade name: Tecipul)
Trazodone (SARI antidepressant/anxiolytic/hypnotic with mild H1 blockade action)
Tripelennamine
Triprolidine

To me, it's not specific enough because it doesn't identify the active ingredient.