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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Non-Standardized Food Allergenic Extract [EPC]
Sloe is a non-standardized allergenic extract used primarily for the diagnosis and treatment of IgE-mediated hypersensitivity to the fruit of the blackthorn bush (Prunus spinosa).
Name
Sloe
Raw Name
SLOE
Category
Non-Standardized Food Allergenic Extract [EPC]
Drug Count
6
Variant Count
6
Last Verified
February 17, 2026
About Sloe
Sloe is a non-standardized allergenic extract used primarily for the diagnosis and treatment of IgE-mediated hypersensitivity to the fruit of the blackthorn bush (Prunus spinosa).
Detailed information about Sloe
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Sloe.
The FDA regulates these extracts under the Public Health Service Act. Sloe allergenic extract is primarily indicated for patients suspected of having a Type I hypersensitivity (immediate-type allergy) to the fruit. This is often relevant in the context of Oral Allergy Syndrome (OAS) or pollen-food allergy syndrome, where individuals sensitized to certain pollens (particularly birch pollen) experience cross-reactivity with fruits in the Rosaceae family, which includes sloe, peaches, cherries, and plums.
At the molecular level, Sloe allergenic extract works by eliciting a controlled immunological response. When the extract is introduced into the skin via prick or intradermal injection, it interacts with specific Immunoglobulin E (IgE) antibodies that are bound to the surface of mast cells and basophils. If the patient is sensitized to Sloe, the allergens in the extract cross-link these IgE antibodies.
This cross-linking triggers a process called degranulation, where the mast cells release inflammatory mediators, most notably histamine, as well as leukotrienes and prostaglandins. These chemicals cause localized vasodilation (widening of blood vessels) and increased capillary permeability. The clinical result is the 'wheal and flare' reaction—a raised, itchy bump (wheal) surrounded by redness (flare). The size of this reaction allows healthcare providers to quantify the level of sensitization. In immunotherapy, the mechanism shifts toward inducing 'immune tolerance' by promoting the production of IgG4 (blocking antibodies) and regulatory T-cells, though Sloe is more commonly used for diagnostic purposes.
The pharmacokinetics of allergenic extracts like Sloe differ significantly from traditional systemic medications because they are administered locally to induce a site-specific immune response.
Sloe allergenic extract is utilized in the following clinical scenarios:
Sloe allergenic extract is typically available in the following formats:
> Important: Only your healthcare provider can determine if Sloe allergenic extract testing is appropriate for your diagnostic workup or if an alternative diagnostic method is required.
Dosage for Sloe allergenic extract is highly individualized and must be determined by an allergy specialist based on the patient's sensitivity levels.
For diagnostic purposes, a single drop of the extract (typically 1:10 or 1:20 w/v concentration) is applied to the skin, followed by a light prick through the drop. A positive control (histamine) and a negative control (saline/glycerin) must be performed simultaneously to ensure the validity of the test results.
If the SPT is negative, an intradermal dose of 0.02 mL to 0.05 mL of a 1:100 or 1:1000 dilution may be injected into the superficial layers of the skin. This method is more sensitive but carries a higher risk of systemic reactions.
Sloe allergenic extract is generally considered safe for use in children, provided it is administered by a pediatric allergist. The procedure for skin testing in children is identical to that in adults, though the number of simultaneous tests may be limited to minimize discomfort. There is no specific age-based 'dose' as the test is qualitative (looking for a reaction) rather than quantitative (systemic drug delivery).
No dosage adjustments are required for renal impairment, as the systemic exposure is minimal. However, patients with end-stage renal disease may have altered skin reactivity (uremic pruritus), which can complicate the interpretation of results.
No dosage adjustments are necessary for patients with liver disease.
Geriatric patients often exhibit reduced skin reactivity due to age-related changes in mast cell density and skin vascularity. Healthcare providers may need to adjust the interpretation of 'positive' results in this population.
Sloe allergenic extract is never for self-administration. It must be administered in a clinical setting equipped to handle anaphylaxis.
In the context of diagnostic testing, a 'missed dose' simply refers to a cancelled appointment. If the patient is undergoing immunotherapy (SCIT) and misses a scheduled injection, the allergist will follow a specific 'build-up' or 'maintenance' schedule adjustment, which may involve repeating the previous dose or reducing the dose depending on the length of the delay.
An 'overdose' in allergy testing occurs if too much extract is injected or if a concentration that is too high is used for an intradermal test.
> Important: Follow your healthcare provider's instructions regarding the discontinuation of antihistamines before the test. Do not attempt to perform skin testing on yourself.
Most patients undergoing testing with Sloe extract will experience local symptoms at the site of administration. These are expected and indicate the test is working:
> Warning: Stop the procedure and call for emergency assistance immediately if you experience any of the following systemic symptoms:
Because diagnostic testing is a one-time or infrequent event, long-term side effects are virtually non-existent. However, for patients receiving Sloe extract as part of long-term immunotherapy, there is a theoretical risk of developing 'Serum Sickness' (a Type III hypersensitivity), though this is extremely rare with modern extracts. Prolonged use of subcutaneous injections can occasionally lead to small areas of subcutaneous atrophy (thinning of the fat layer) at the injection site.
While Sloe extract itself may not have a specific product-named Black Box Warning, the entire class of Allergenic Extracts carries a general warning regarding the risk of severe systemic reactions.
FDA Class Warning Summary:
Report any unusual symptoms, especially those occurring several hours after leaving the clinic, to your healthcare provider immediately.
Sloe allergenic extract is a potent biological product. Safety is dependent on proper administration and patient selection. It is vital that patients provide a full medical history, including all current medications and any history of severe allergic reactions to fruits or pollens.
No specific FDA black box warning exists uniquely for Sloe, but it falls under the mandatory class warnings for all allergenic extracts. These warnings emphasize that the product is intended for use only by clinicians prepared to manage anaphylaxis. The warning also notes that the potency of non-standardized extracts can vary between manufacturers and even between different lots from the same manufacturer.
Generally, Sloe testing does not affect the ability to drive. However, if a patient experiences a vasovagal reaction (fainting) or a systemic reaction requiring medication like diphenhydramine (which causes drowsiness), they should not drive until the effects have fully resolved.
Alcohol should be avoided for at least 24 hours before and after testing. Alcohol can increase peripheral blood flow and potentially enhance the rate of allergen absorption or exacerbate a systemic reaction.
There is no 'withdrawal' from Sloe extract. However, if a patient is undergoing immunotherapy and decides to stop, they will lose the protective immune tolerance they have built up over time.
> Important: Discuss all your medical conditions, especially respiratory and heart conditions, with your healthcare provider before starting Sloe testing.
Sloe extract testing does not typically interfere with standard blood labs (CBC, metabolic panel). However, it will obviously interfere with other allergy tests performed on the same day if the reactions are large enough to overlap.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, especially those for allergies, depression, or blood pressure.
Patients with a known allergy to Birch Pollen (Betula verrucosa) often show cross-sensitivity to Sloe due to the presence of homologous proteins (e.g., Bet v 1-related proteins). Similarly, those allergic to other members of the Rosaceae family (almonds, apples, pears) may react to Sloe extract even without prior direct exposure to the fruit.
> Important: Your healthcare provider will evaluate your complete medical history, including your current respiratory status, before prescribing or administering Sloe extract.
Sloe allergenic extract is classified as Pregnancy Category C (under the older FDA system). There are no adequate and well-controlled studies in pregnant women. The primary risk is not the extract itself, but the potential for a systemic reaction (anaphylaxis). Anaphylaxis during pregnancy is a medical emergency that can lead to uterine contractions, placental abruption, and fetal distress due to lack of oxygen. Consequently, diagnostic skin testing for Sloe is usually postponed until after delivery unless the information is critical for immediate management.
It is not known whether the allergenic components of Sloe extract are excreted in human milk. However, since the proteins are digested in the infant's gut if they were present, the risk to a nursing infant is considered extremely low. The main consideration is the mother's safety during the procedure.
Sloe extract is used in children as young as infants, though skin reactivity is less reliable in children under 2 years of age. Pediatric testing requires a modified approach, often using fewer allergens and ensuring the child is distracted to prevent movement during the 20-minute wait. The safety profile in children is similar to that in adults, with local reactions being the most common side effect.
In patients over 65, the skin's 'mast cell response' is often diminished. This can lead to smaller wheal sizes, which may be misinterpreted as a negative result. Furthermore, elderly patients are more likely to have underlying cardiovascular disease, making them more vulnerable to the stress of a systemic reaction or the side effects of epinephrine if it must be administered.
There is no evidence that renal impairment alters the response to Sloe extract. However, patients on dialysis may have 'itchy skin' (uremic pruritus) which can make the interpretation of a skin test difficult. No dose adjustment is required.
Liver disease does not affect the IgE-mediated response on the skin. No adjustments are necessary for patients with hepatic impairment.
> Important: Special populations require individualized medical assessment to ensure that the diagnostic benefits of Sloe testing outweigh the potential risks.
Sloe allergenic extract functions as an antigenic stimulus. The extract contains a complex mixture of proteins, glycoproteins, and polysaccharides derived from the Prunus spinosa fruit. The primary mechanism involves the binding of these exogenous allergens to Sloe-specific IgE antibodies anchored to the high-affinity FceRI receptors on mast cells in the skin's dermis. This binding causes receptor aggregation, leading to an influx of calcium ions and the subsequent degranulation of the mast cell. The released mediators (histamine, etc.) act on H1 receptors on local blood vessels to cause the characteristic wheal and flare.
The pharmacodynamic effect is strictly local and dose-dependent based on the concentration of the extract. The onset of the 'wheal' reaction is typically 5-10 minutes, peaking at 15-20 minutes. The duration of the visible skin reaction is usually 60-120 minutes, after which the mediators are metabolized and the fluid is reabsorbed into the lymphatic system.
| Parameter | Value |
|---|---|
| Bioavailability | Negligible (Local) |
| Protein Binding | Local Tissue Binding High |
| Half-life | < 2 hours (Local effect) |
| Tmax | 15-20 minutes (Skin reaction) |
| Metabolism | Local Proteolysis |
| Excretion | Renal (as peptides) |
Sloe belongs to the Non-Standardized Allergenic Extract class. It is grouped with other food extracts like peach, pear, and plum extracts. It is distinct from standardized extracts like Dermatophagoides farinae (dust mite) or Phleum pratense (timothy grass), which have standardized biological potency units.
Medications containing this ingredient
Common questions about Sloe
Sloe allergenic extract is primarily used by allergists to diagnose a specific allergy to sloe berries, which are the fruit of the blackthorn bush. It is used in skin prick testing or intradermal testing for patients who experience allergic symptoms like itching or swelling after eating sloe-containing products. The test helps determine if the reaction is a true IgE-mediated allergy rather than a simple food intolerance. It is also used to assess cross-reactivity in patients allergic to other stone fruits in the Rosaceae family. Only a qualified healthcare professional can perform these tests.
The most common side effects of Sloe extract testing are localized to the area where the test was performed. Most patients will experience a 'wheal and flare' reaction, which consists of a small, itchy, raised bump and surrounding redness. This is a normal part of the testing process and usually disappears within one to two hours. Some patients may experience a delayed reaction where swelling returns several hours later. While rare, systemic symptoms like hives or lightheadedness can occur and require medical attention.
It is generally advised to avoid alcohol for at least 24 hours before and after an allergy test with Sloe extract. Alcohol can increase blood flow to the skin and may cause flushing, which makes it difficult for the doctor to accurately read the test results. Furthermore, alcohol can potentially worsen a systemic allergic reaction if one were to occur. Always follow the specific pre-test instructions provided by your allergy clinic. If you have consumed alcohol recently, inform your doctor before the test begins.
Allergy testing with Sloe extract is typically avoided during pregnancy as a precautionary measure. While the extract does not directly harm the fetus, a severe allergic reaction (anaphylaxis) in the mother could lead to a dangerous drop in blood pressure and reduced oxygen delivery to the baby. Most allergists recommend waiting until after delivery to perform elective skin testing. If an allergy diagnosis is absolutely necessary during pregnancy, blood tests (IgE testing) are usually preferred over skin testing. Discuss the risks and benefits with your obstetrician and allergist.
In the context of a skin test, Sloe extract works very quickly. A visible reaction usually begins to develop within 5 to 10 minutes of the skin being pricked. The reaction typically reaches its maximum size (peak effect) between 15 and 20 minutes. This is when the healthcare provider will measure the size of the wheal and flare to determine the result. If the test is being used for immunotherapy, it can take several months of regular injections before a patient notices a reduction in their allergy symptoms.
Since Sloe is most commonly used as a one-time diagnostic test, 'stopping' it is not usually an issue. However, if you are receiving Sloe extract as part of an immunotherapy (allergy shot) program, stopping suddenly will result in a gradual loss of the allergic tolerance you have built up. You will not experience 'withdrawal' symptoms, but your original allergy symptoms may return upon exposure to sloe berries. Always consult your allergist before discontinuing a long-term immunotherapy treatment plan.
If you miss an appointment for a Sloe diagnostic skin test, you simply need to reschedule with your doctor's office. If you are on an immunotherapy schedule and miss a dose, contact your allergist immediately. They will determine how to adjust your next dose based on how many days or weeks have passed since your last injection. Do not attempt to 'double up' on doses or administer the extract yourself. Consistency is key for immunotherapy to be effective and safe.
There is no evidence to suggest that Sloe allergenic extract causes weight gain. The amount of the extract used in diagnostic testing is minuscule and does not have systemic metabolic effects. Even in long-term immunotherapy, the proteins in the extract do not influence appetite or fat storage. If you experience weight changes while undergoing allergy treatment, it is likely due to other factors or medications, such as oral steroids, and should be discussed with your healthcare provider.
Sloe extract can interact with several medications, particularly those that affect the immune response or the body's reaction to adrenaline. Antihistamines, certain antidepressants, and some sleep aids must be stopped several days before testing because they can hide a positive result. More importantly, beta-blockers used for heart conditions can make it difficult to treat a severe reaction if one occurs. Always provide your allergist with a complete list of all medications, including over-the-counter supplements, before undergoing any testing.
Allergenic extracts like Sloe are biological products rather than simple chemical drugs, so the term 'generic' is not used in the same way. However, Sloe extract is produced by several different biological laboratories. While the extracts from different companies are similar, they are 'non-standardized,' meaning the potency might vary between brands. Your allergist will typically stick with one manufacturer's product during your treatment to ensure consistency in your results and safety.