Allergic reactions to clove, its component eugenol have been reported, including possible severe reactions (anaphylaxis). Signs of allergy may include rash, itching or shortness of breath. Eugenol or clove can cause allergic rashes when applied to skin or inside the mouth. Hives have been reported in clove cigarette smokers. Individuals with known allergy to clove, its component eugenol, or to Balsam of Peru should avoid the use of clove by mouth, inhaled from cigarettes, or applied to the skin.

Clove is generally regarded as safe for food use in the United States. However, when clove is taken by mouth in large doses, in its undiluted oil form, or used in clove cigarettes, side effects may occur including vomiting, sore throat, seizure, sedation, difficulty breathing, fluid in the lungs, vomiting of blood, blood disorders, kidney failure, and liver damage or failure. People with kidney or liver disorders or who have had seizures should avoid clove. Serious side effects are reported more often in young children, even with small doses, and therefore clove supplements should be avoided in children and pregnant or nursing women.

Clove or clove oil may cause an increased bleeding risk, based largely on laboratory research. Caution is advised in patients with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary. It is not clear what doses or methods of using clove may increase this risk. Clove use should be stopped before surgery.

When applied to the skin or inside of the mouth, clove can cause burning, loss of sensation or painful sensation, local tissue damage, dental pulp damage, higher risk of cavities, or sore lips. Undiluted clove oil has a high risk of causing contact dermatitis (rash) and even burns if applied to the skin at full strength. The application of clove combination herbal creams to the penis has been said to cause episodes of difficulty with erection or ejaculation.

Clove oil taken by mouth may lower blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.

Contamination can occur if clove is improperly stored.

Not enough information about safety is available to recommend the use of clove supplements in pregnant or breastfeeding women.

There is not enough scientific evidence available to recommend a specific dose of clove by mouth, on the skin, or by any other route.

There is not enough scientific evidence available to recommend a specific dose of clove by mouth, on the skin, or by any other route.

Based on laboratory research, clove theoretically may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. It is not clear what doses or methods of using clove may increase this risk. Some examples of drugs that increase bleeding risk include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

Clove oil taken by mouth may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary.

When applied to the skin, eugenol, a component of clove, may reduce the ability to feel and react to painful stimulation. Therefore, use of clove products on the skin with other numbing or pain-reducing products such as lidocaine/prilocaine cream (Emla®) theoretically may increase effects.

Clove may also react with antifungals, anti-inflammatories, antihistamines, antineoplastics, and drugs taken for cardiovascular conditions. Clove may also affect the way in which the liver breaks down certain drugs.

Based on laboratory research, clove may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. It is not clear what doses or methods of using clove may increase this risk. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, some cases with garlic, and fewer cases with saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.

Clove may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.

When applied to the skin, eugenol, a component of clove, may reduce the ability to feel and react to painful stimulation. Therefore, use with other numbing or pain-reducing products such as capsaicin cream (Zostrix®) may in theory cause exaggerated effects.

Clove may also react with anti-inflammatory, antifungal, antihistamine, and antineoplastic herbs, and herbs taken for cardiovascular conditions. Clove may also affect the way in which the liver breaks down certain herbs.