Based on the information available, there can be potential drug interactions when combining Lipitor (atorvastatin) with certain allergy medications. However, it's important to note that not all allergy medications will interact with Lipitor. The likelihood of an interaction depends on the specific allergy medication in question.

Lipitor is a statin, a class of drugs used to lower cholesterol levels. According to the Lipitor Prescribing Information, atorvastatin is metabolized by several cytochrome P450 isoforms, including CYP3A4, CYP2C9, and CYP2C19. Therefore, medications that inhibit these enzymes can increase the concentration of atorvastatin in the body, potentially leading to adverse effects.

Allergy medications that contain antihistamines, such as diphenhydramine (Benadryl), loratadine (Claritin), or cetirizine (Zyrtec), are less likely to interact with Lipitor. However, some allergy medications contain corticosteroids, such as prednisone or dexamethasone, which can increase the risk of muscle damage (myopathy) when combined with Lipitor.

Additionally, some allergy medications contain nasal decongestants, such as pseudoephedrine or phenylephrine, which can increase blood pressure. Since Lipitor can also increase the risk of developing high blood pressure, combining these medications may exacerbate this effect.

Therefore, it's crucial to consult with a healthcare provider or pharmacist before combining Lipitor with any medication, including allergy medications. They can provide personalized advice based on an individual's medical history and current medications.

Sources:

1. Lipitor Prescribing Information. Pfizer. <https://www.accessdata.fda.gov/drugsatfda_docs/label/2016/020272s054,020580s030,020882s025,021103s023lbl.pdf>
2. DrugPatentWatch.com. Atorvastatin. <https://www.drugpatentwatch.com/drugs/atorvastatin>