The side effects of penicillin can be altered by taking other medications at the same time. Taking oral contraceptives along with penicillin may lower the effects of the contraceptive. When probenecid is used concurrently with penicillin, kidney excretion of probenecid is increase resulting in higher blood levels of penicillin in the circulation. In some instances, this would be intended therapeutic effect. In other instances, this is an unintended side effect. Neomycin can lower the absorption of penicillin from the gastrointestinal tract resulting in lower than expected levels of penicillin in the circulation. This side effect may result in an ineffective therapeutic effect of penicillin. When methotrexate is administered with penicillin, toxicity may occur related to methotrexante.

Allergen immunotherapy is useful for environmental allergies, allergies to insect bites, and asthma. Its benefit for food allergies is unclear and thus not recommended. Immunotherapy involves exposing people to larger and larger amounts of allergen in an effort to change the immune system's response.

Meta-analyses have found that injections of allergens under the skin is effective in the treatment in allergic rhinitis in children and in asthma. The benefits may last for years after treatment is stopped. It is generally safe and effective for allergic rhinitis and conjunctivitis, allergic forms of asthma, and stinging insects.

The evidence also supports the use of sublingual immunotherapy for rhinitis and asthma but it is less strong. For seasonal allergies the benefit is small. In this form the allergen is given under the tongue and people often prefer it to injections. Immunotherapy is not recommended as a stand-alone treatment for asthma.

An experimental treatment, enzyme potentiated desensitization (EPD), has been tried for decades but is not generally accepted as effective. EPD uses dilutions of allergen and an enzyme, beta-glucuronidase, to which T-regulatory lymphocytes are supposed to respond by favoring desensitization, or down-regulation, rather than sensitization. EPD has also been tried for the treatment of autoimmune diseases but evidence does not show effectiveness.

A review found no effectiveness of homeopathic treatments and no difference compared with placebo. The authors concluded that, based on rigorous clinical trials of all types of homeopathy for childhood and adolescence ailments, there is no convincing evidence that supports the use of homeopathic treatments.

According to the NCCIH, the evidence is relatively strong that saline nasal irrigation and butterbur are effective, when compared to other alternative medicine treatments, for which the scientific evidence is weak, negative, or nonexistent, such as honey, acupuncture, omega 3's, probiotics, astragalus, capsaicin, grape seed extract, Pycnogenol, quercetin, spirulina, stinging nettle, tinospora or guduchi.

When penicillin is used at high doses hypokalemia, metabolic acidosis, and hyperkalemia can occur. Developing hypernatremia after administering high doses of penicillin can be a serious side effect.

Antihistamine drugs can be taken orally and nasally to control symptoms such as sneezing, rhinorrhea, itching, and conjunctivitis.

It is best to take oral antihistamine medication before exposure, especially for seasonal allergic rhinitis. In the case of nasal antihistamines like azelastine antihistamine nasal spray, relief from symptoms is experienced within 15 minutes allowing for a more immediate 'as-needed' approach to dosage.

Ophthalmic antihistamines (such as azelastine in eye drop form and ketotifen) are used for conjunctivitis, while intranasal forms are used mainly for sneezing, rhinorrhea, and nasal pruritus.

Antihistamine drugs can have undesirable side-effects, the most notable one being drowsiness in the case of oral antihistamine tablets. First-generation antihistamine drugs such as diphenhydramine cause drowsiness, but second- and third-generation antihistamines such as cetirizine and loratadine are less likely to cause this problem.

Pseudoephedrine is also indicated for vasomotor rhinitis. It is used only when nasal congestion is present and can be used with antihistamines. In the United States, oral decongestants containing pseudoephedrine must be purchased behind the pharmacy counter by law in effort to prevent the making of methamphetamine.

Intranasal corticosteroids are used to control symptoms associated with sneezing, rhinorrhea, itching, and nasal congestion. Steroid nasal sprays are effective and safe, and may be effective without oral antihistamines. They take several days to act and so must be taken continually for several weeks, as their therapeutic effect builds up with time.

In 2013, a study compared the efficacy of mometasone furoate nasal spray to betamethasone oral tablets for the treatment of people with seasonal allergic rhinitis and found that the two have virtually equivalent effects on nasal symptoms in people.

Systemic steroids such as prednisone tablets and intramuscular triamcinolone acetonide or glucocorticoid (such as betamethasone) injection are effective at reducing nasal inflammation, but their use is limited by their short duration of effect and the side-effects of prolonged steroid therapy.

Antihistamines such as diphenhydramine and chlorpheniramine are commonly used as treatment. People treated with H1 antihistamines exhibit reduced production of histamine and leukotrienes as well as downregulation of adhesion molecule expression on the vasculature which in turn attenuates allergic symptoms by 40–50%.

Dual-action medications are also prescribed frequently. Olopatadine (Patanol) and ketotifen fumarate (Alaway or Zaditor) both provide protection by acting as an antihistamine and a mast cell stabilizer together. Patanol is a prescription medication, whereas ketotifen fumarate is not.

A systematic review of 30 trials, with 17 different treatment comparisons found that all topical antihistamines and mast cell stabilizers included for comparison were effective in reducing symptoms of seasonal allergic conjunctivitis. There was not enough evidence to determine differences in long-term efficacy among the treatments.

Many of the eye drops can cause burning and stinging, and have side-effects. Proper eye hygiene can improve symptoms, especially with contact lenses. Avoiding precipitants, such as pollen or mold can be preventative.

Mast cell stabilizers can help people with allergic conjunctivitis. They tend to have delayed results, but they have fewer side-effects than the other treatments and last much longer than those of antihistamines. Some people are given an antihistamine at the same time so that there is some relief of symptoms before the mast cell stabilizers becomes effective. Doctors commonly prescribe lodoxamide and nedocromil as mast cell stabilizers, which come as eye drops.

A mast cell stabilizer is a class of non-steroid controller medicine that reduces the release of inflammation-causing chemicals from mast cells. They block a calcium channel essential for mast cell degranulation, stabilizing the cell, thus preventing the release of histamine. Decongestants may also be prescribed. Another common mast cell stabilizer that is used for treating allergic conjunctivitis is sodium cromoglicate.

Epinephrine is another name for the hormone adrenaline, which is produced naturally in the body. An epinephrine injection is the first-line treatment for severe allergic reactions (anaphylaxis). If administered in a timely manner, epinephrine can reverse its effects.

Epinephrine relieves airway swelling and obstruction, and improves blood circulation; blood vessels are tightened and heart rate is increased, improving circulation to body organs. Epinephrine is available by prescription in an autoinjector.

Antihistamines can alleviate some of the milder symptoms of an allergic reaction, but do not treat all symptoms of anaphylaxis. Antihistamines block the action of histamine, which causes blood vessels to dilate and become leaky to plasma proteins. Histamine also causes itchiness by acting on sensory nerve terminals. The most common antihistamine given for food allergies is diphenhydramine.

Cat allergies can often be controlled with over the counter or prescription medications. Antihistamines and decongestants may provide allergy relief.

Treatment for accidental ingestion of milk products by allergic individuals varies depending on the sensitivity of the person. An antihistamine such as diphenhydramine (Benadryl) may be prescribed. Sometimes prednisone will be prescribed to prevent a possible late phase Type I hypersensitivity reaction. Severe allergic reactions (anaphalaxis) may require treatment with an epinephrine pen, i.e., an injection device designed to be used by a non-healthcare professional when emergency treatment is warranted. A second dose is needed in 16-35% of episodes.

There is active research on trying oral immunotherapy (OIT) to desensitize people to egg allergens. A Cochrane Review concluded that OIT can desensitize people, but it remains unclear whether long-term tolerance develops after treatment ceases, and 69% of the people enrolled in the trials had adverse effects. They concluded there was a need for standardized protocols and guidelines prior to incorporating OIT into clinical practice. A second review noted that allergic reactions, up to anaphylaxis, can occur during OIT, and recommends this treatment not be routine medical practice. A third review limited its scope to trials of baked egg-containing goods such as bread or cake as a means of resolving egg allergy. Again, there were some successes, but also some severe allergic reactions, and the authors came down on the side of not recommending this as treatment.

Some allergy sufferers find relief in allergen immunotherapy, a periodic injection therapy designed to stimulate the body's natural immune responses to the cat allergens.

Treatment for accidental ingestion of soy products by allergic individuals varies depending on the sensitivity of the person. An antihistamine such as diphenhydramine (Benadryl) may be prescribed. Sometimes prednisone will be prescribed to prevent a possible late phase Type I hypersensitivity reaction. Severe allergic reactions (anaphalaxis) may require treatment with an epinephrine pen, i.e., an injection device designed to be used by a non-healthcare professional when emergency treatment is warranted. A second dose is needed in 16-35% of episodes.

The need for a dairy-free diet should be reevaluated every six months by testing milk-containing products low on the "milk ladder", such as fully cooked, i.e., baked foods containing milk, in which the milk proteins have been denatured, and ending with fresh cheese and milk. Desensitization via oral immunotherapy holds some promise but is still being actively researched (see Research).

Treatment for accidental ingestion of milk products by allergic individuals varies depending on the sensitivity of the person. An antihistamine such as diphenhydramine (Benadryl) may be prescribed. Sometimes prednisone will be prescribed to prevent a possible late phase Type I hypersensitivity reaction. Severe allergic reactions (anaphalaxis) may require treatment with an epinephrine pen, i.e., an injection device designed to be used by a non-healthcare professional when emergency treatment is warranted. A second dose is needed in 16-35% of episodes.

Currently there is no cure for allergic reactions to peanuts other than strict avoidance of peanuts and peanut-containing foods. Extra care needed for food consumed at or purchased from restaurants. The principal treatment for anaphylaxis is epinephrine as an injection.

Avoiding allergens will help prevent symptoms. Allergies that a child has to the family pet can be controlled by removing the animal and finding it a new home. Exterminating cockroaches, mice and rats and a thorough cleaning can reduce symptoms of an allergy in children. Dust mites are attracted to moisture. They consume human skin that has come off and lodged in, furniture, rugs, mattresses, box springs, and pillows. The child's bedding can be covered with allergen-proof covers. Laundering of the child's clothing, bed linens and blankets will also reduce exposure.

Exposure to allergens outside the home can be controlled with the use of air conditioners. Washing the hair, taking a bath or shower before bedtime can be done to remove allergens that have been picked up from outside the home. If grass or grass pollen is an allergen it is sometimes beneficial to remain indoors while grass is being cut or mowed. Children with allergies to grass can avoid playing in the grass to prevent allergic symptoms. Staying out of piled leaves in the fall can help. Pets returning into the home after being outdoors may track in allergens.

Immunotherapy involves attempts to reduce or eliminate allergic sensitivity by repeated exposure. This active research concept involves swallowing small amounts of peanuts, holding a peanut product under the tongue - sublingual immunotherapy - skin patches or injections. None of these are considered ready for use in people outside of carefully conducted trials. In those with mild peanut allergies, gradually eating more and more peanuts resulted in at least some short-term benefits. Due to the amount of evidence being small and the high rate of adverse effects, this is not currently recommended as treatment. Sublingual immunotherapy involves putting gradually increasing doses of an allergy extract under a person's tongue. The extract is then either spat or swallowed. It is not currently recommended as treatment; however, it is being studied. Epicutaneous immunotherapy involves giving the allergen through a patch. Trials are ongoing.

Most people find it necessary to strictly avoid any item containing dairy ingredients. Milk from other species (goat, sheep...) should not be substituted for cow's milk, as milk proteins from other mammals are often cross-reactive. Beyond the obvious (anything with milk, cheese, cream, butter or yogurt in the name), food ingredient lists need to be examined:

- Ghee

- Some Margarine (!)

- Medical food beverages (Ensure, etc.)

- "Non-dairy" coffee creamer

- Eggnog

- Sherbet

- "Cream of..." soups

- Creamy pasta sauces

- Creamy salad dressings

- Nutella

- Simplesse

- Bread

- Baked goods

- Crackers

- Cereals

- Some Chewing gum (!)

- Some Hot dogs (!)

- Instant mashed potatoes

- Flavored potato chips

- Caramel and nougat candy

- casein (milk protein

- whey (milk protein)

- Lactalbumin (milk protein)

- lactoglobulin (milk protein)

- lactoferrin (milk protein)

Probiotic products have been tested, and some found to contain milk proteins which were not always indicated on the labels.

Some symptoms might weaken if people get allergy shots. After getting several treatments for a long time, some allergic people will not have reactions afterwards.

Some reactions have been eased by replacing original rice with genetically modified rice. This is regarded as a new choice for rice allergic people.

Reactions might lessen by staying away from rice long-term.

OAS must be managed in conjunction with the patient's other allergies, primarily the allergy to pollen. The symptom severity may wax and wane with the pollen levels. Published pollen counts and seasonal charts are useful but may be ineffective in cases of high wind or unusual weather, as pollen can travel hundreds of kilometers from other areas.

In addition, patients are advised to avoid the triggering foods, particularly nuts.

Peeling or cooking the foods has been shown to eliminate the effects of some allergens such as "mal d 1" (apple), but not others such as celery or strawberry. In the case of foods such as hazelnut, which have more than one allergen, cooking may eliminate one allergen but not the other.

Antihistamines may also relieve the symptoms of the allergy by blocking the immune pathway. Persons with a history of severe anaphylactic reaction may carry an injectable emergency dose of epinephrine (such as an EpiPen). Oral steroids may also be helpful. Allergy immunotherapy has been reported to improve or cure OAS in some patients. Immunotherapy with extracts containing birch pollen may benefit OAS sufferers of apple or hazelnut related to birch pollen-allergens. Even so, the increase in the amount of apple/hazelnut tolerated was small (from 12.6 to 32.6 g apple), and as a result, a patient's management of OAS would be limited.

Management of wheat allergy consists of complete withdrawal of any food containing wheat and other gluten-containing cereals (gluten-free diet). Nevertheless, some patients can tolerate barley, rye or oats.

In people suffering less severe forms of wheat-dependent exercise induced anaphylaxis (WDEIA), may be enough completely avoiding wheat consumption before exercise and other cofactors that trigger disease symptoms, such as nonsteroidal anti-inflammatory drugs and alcohol.

Wheat is often a cryptic contaminant of many foods; more obvious items are bread crumbs, maltodextrin, bran, cereal extract, couscous, cracker meal, enriched flour, gluten, high-gluten flour, high-protein flour, seitan, semolina wheat, vital gluten, wheat bran, wheat germ, wheat gluten, wheat malt, wheat starch or whole wheat flour. Less obvious sources of wheat could be gelatinized starch, hydrolyzed vegetable protein, modified food starch, modified starch, natural flavoring, soy sauce, soy bean paste, hoisin sauce, starch, vegetable gum, specifically Beta-glucan, vegetable starch.

Completely eliminating salicylate from one's diet and environment is virtually impossible and is not a recommended course of action by many immunologists. The range of foods that have no salicylate content is very limited, and consequently salicylate-free diets are very restricted.

Desensitization involves daily administration of progressive doses of salicylate. This process is usually performed as an inpatient, with a crash-cart at the bedside over a six-day period, beginning with 25 mg of I.V. lysine-aspirin and progressing to 500 mg if tolerated.

Montelukast is one form of treatment used in aspirin-intolerant asthma.

Once a nickel allergy is detected, the best treatment is avoidance of nickel-releasing items. It is important to know the main items that can cause nickel allergy, which may be remembered using the mnemonic "BE NICKEL AWARE". The top 13 categories that contain nickel include beauty accessories, eyeglasses, money, cigarettes, clothes, kitchen and household, electronics and office equipment, metal utensils, aliment, jewelry, batteries, orthodontic and dental appliances, and medical equipment. Other than strict avoidance of items that release free nickel, there are other treatment options for reduction of exposure. The first step is to limit friction between skin and metallic items. Susceptible people may try to limit sweating while wearing nickel items, to reduce nickel release and thus decrease chances for developing sensitization and/or allergy. Another option is to shield electronics, metal devices, and tools with fabric, plastic, or acrylic coverings. Dermatological application tests has shown that barrier creams effectively prevent the symptoms of nickel allergy, such as the Nidiesque™.

There are test kits that can be very helpful to check for nickel release from items prior to purchasing. The ACDS providers can give a guidance list of safe items. In addition to avoidance, healthcare providers may prescribe additional creams or medications to help relieve the skin reaction.