What are Food allergy and Food intolerance

Many people assign their variety of symptoms to food, and many such victims are seen and started on exclusion diets. The scientific proof that food does damage in most instances is feeble, although unfavorable reactions to food definitely exist. These can be classified into those that involve immune mechanisms as “food allergy” and those that do not involve immune mechanism as “food intolerance”.


Food allergy

Food allergy affect up to about 5% of young children and about 1-2% of adults. This form of allergy may be IgE mediated or non-IgE mediated (T-cell mediated). The IgE mediated reactions occurs within minutes or hour after the ingestion of the food . Adults are more likely to be allergic to fish, shellfish and peanuts, while young children are mostly allergic to cow's milk, egg white, wheat, and soy. Peanuts are very allergenic and when it is there it persists throughout life. The following conditions can result from food allergy


Acute hypersensitivity: After ingestion of nuts, strawberries or shellfish the patient suffers from urticaria , vomiting and diarrhea. These normally don’t pose much problem as the patients are aware and learn to avoid the suspected food. Unintentional eating of the incriminating foodstuff can sometimes occur, leading to angioneurotic oedema, a life threatening condition.

Eczema and asthma: Mostly IgE mediated and affect the children.

Rhinitis and asthma: In the atopic individuals these are mostly produced by milk and chocolates.

Chronic urticaria: Exclusion of particular food releive the problem in most patients

Food-sensitive enteropathy: Coeliac disease (gluten (wheat) sensitive enteropathy), and cow's milk enteropathy (in infants) are the example of this reaction.


Food intolerance

Migraine: Intake of foods like chocolate, cheese and alcohol Some patients suffer from migraine. These foods are rich in certain amines, such as tyramine, which are responsible for such attacks. Those on monoamine oxidase inhibitors, which are involved in the metabolism of these amines, are particularly susceptible.

Irritable bowel syndrome: Though mechanism not clearly understood, certain food precipitates the attack of IBS following ingestion of certain food items, such as wheat.

Chinese restaurant syndrome: dizziness, faintness, nausea, sweating and chest pains may follow after ingestion of Chinese food in some. The responsible agent is Monosodium glutamate, a flavoring agent used in cooking Chinese food.

Lactose intolerance: Abdominal bloating and diarrhea following intake of milk is probably the commonest form of food intolerance all over the world. Lactose present in the milk is the causative factor. This may be genetic in origin

Phenylketonuria: This is also a type of food intolerance, and is due to missing phenylalanine hydroxylase, which is essential for the metabolism of phenylalanine in the protein of the diet

There are other genetic errors of metabolism, which can be regarded as forms of food intolerance.

Food intolerance can occur:

To any constituent of food like the histamine in mackerel or canned food, or the tyramine in cheese.

Or,

Chemical mediators released by food stuff like histamine may be released by tomatoes or strawberries.

Or,

Toxic chemicals present in food like the food additive tartrazine.

Though sometimes thought, there are no evidence to prove that conditions such as arthritis, behavior and affective disorders and Crohn's disease are because of certain type of food ingestion. Multiple vague symptoms such as tiredness or malaise as sometimes blamed are not due to food allergy. Mostly, these patients are victim of some form of psychiatric disorder.


Treatment of food allergies and intolerance:

A careful history may help to outline the contributory mediator, particularly when the effects are instant.

Skin-prick testing with allergen, measurement of antigen or antibodies in the do not correlate with the symptoms and results are usually misleading. 'Fringe' techniques like hair analysis, has negligible value, though advised widely.

Diagnostic exclusion diets are useful but very time-consuming. They can sporadically be of value in recognizing a particular food causing allergy or intolerance.

Dietary challenge is a method where food and the test being given sublingually or by inhalation in an attempt to reproduce the symptoms. Again this may be helpful in small number of cases.

Most people who have acute allergies to food identify it and stop taking the food, and do not usually require medical treatment. In rest of the patients, a small number seem to be helped by modifying their diet, but there is no good scientific substantiation to prove these exclusion diets.

Migraine - Symptoms, Diagnosis and Treatment

Migraine is recurrent headache associated with visual and gastrointestinal disturbance. The borderline between migraine and tension headaches is vague. Over 12% of any population world-wide report these symptoms.


Mechanisms of migraine

Precise mechanisms of migraine remain unknown. Genetic factors play some part . The headache of migraine, often throbbing, is due to vasodilatation or oedema of blood vessels, with stimulation of nearby nerve endings. Release of vasoactive substances such as nitric oxide has a role . Serum 5 – hydroxytryptamine (5HT) rises with initial symptoms and falls during the headache. Cerebral features, such as tingling limbs, aphasia and weakness, are caused by focal depression of cortical function.


Some patients recognize precipitating factors:

#Week-end migraine (a time of relaxation)
#Chocolate (high in phenylethylamine)
#Cheese (high in tyramine)
#Noise and irritating lights
#With premenstrual symptoms.


Migraine is common around puberty and at the menopause and sometimes increases in severity or frequency with hormonal contraceptives, in pregnancy and with the onset of hypertension. There is no reason to suppose that the development of migraine is suggestive of any serious intracranial lesion. However, since migraine is so common, an intracranial mass and migraine sometimes occur together by coincidence. Migraine sometimes follows a blow to the head - often minor.


Symptoms of Migraine

Migraine attacks vary from intermittent headaches indistinguishable from tension headaches to discrete episodes that mimic thromboembolic cerebral ischaemia.
Distinction between variants is somewhat artificial.
Migraine can be separated into phases:
# initial or, prodromal symptoms
# the main attack (headache, nausea, vomiting)
# sleep and feeling drained afterwards.

Types of Migraine

Migraine with aura (classical migraine)

Prodromal symptoms are usually visual and related to depression of visual cortical function or retinal function. Unilateral patchy scotomata (retina) (Patchy blindness), hemianopic symptoms (cortex), teichopsia (flashes) and fortification spectra (jagged lines resembling battlements) are common. Transient aphasia (Unable to speak) sometimes occurs, with tingling, numbness, vague weakness of one side and nausea. The prodrome persists for a few minutes to about an hour.
Headache then follows. This is occasionally hemicranial (i.e. splitting the head) but often begins locally and becomes generalized. Nausea increases and vomiting follows. The patient is irritable and prefers a darkened room. Superficial temporal arteries are engorged and pulsating. After several hours the migraine settles, sometimes with a diuresis. Deep sleep often ensues.

Migraine without aura (common migraine)

This is the usual variety. Prodromal visual symptoms are vague. There is recurrent headache accompanied by nausea and malaise.

Basilar migraine

Prodromal symptoms include circumoral and tongue tingling, vertigo, diplopia, transient visual disturbance (even blindness), syncope, dysarthria and ataxia. These occur alone or progress to a typical migraine.

Hemiparetic migraine

This rarity is classical migraine with hemiparetic features, i.e. resembling a stroke but with recovery within 24 hours. Exceptionally, cerebral infarction (stroke) occurs.

Ophthalmoplegic migraine

This rarity is a third nerve, or exceptionally a sixth nerve, palsy with a migraine - and difficult to diagnose without investigation to exclude other conditions.

Facioplegic migraine

This is unilateral facial weakness during a migraine.


The diseases, which should be differentiated from migraine

The sudden headache may resemble meningitis or SAH(Sub Arachnoid Haemorrhage). Hemiplegic, visual and hemi sensory symptoms must be distinguished from thromboembolic TIAs(Transient Ischaemic Attacks). In TIAs maximum deficit is present immediately and headache is unusual. Unilateral tingling or numbness may resemble sensory epilepsy (partial seizures). In epilepsy, distinct march (progression) of symptoms is usual.

Treatment of Migraine

#reassurance and relief of anxiety
#avoidance of dietary factors - rarely helpful.

Patients taking hormonal contraceptives may benefit from a brand change, or trying without. Premenstrual migraine may respond to diuretics. Depot oestrogens are sometimes used. Severe hemiplegic symptoms are an indication for stopping hormonal contraceptives.

During an attack. After ruling out any serious cause for a sudden headache, paracetamol or other simple analgesics should be given, with an antiemetic such as metoclopramide if necessary. Repeated use of analgesics leads to further headaches.

Triptans (5-HT, agonists) are also helpful. In some 30% of cases, where there is
recurrent severe migraine, sumatriptan, zolmitriptan, naratriptan and rizatriptan are of value either by prompt self-administered subcutaneous injection, or orally by wafer or inhaler. Triptans should be avoided when there is vascular disease, and not overused.

Prophylaxis of Migraine attack

It is difficult to discern placebo effects of prophylactic drugs. The following are used when attacks are frequent:

#pizotifen (antihistamine and 5-HT antagonist) 0.5 mg at night for several days, increasing to 1.5 mg (common side-effects: weight gain and drowsiness)
#propranolol 10 mg three times daily, increasing to 40-80 mgthree times daily
#amitriptyline: 10 mg(or more) at night.
#Sodium valproate, methysergide, SSRIs, verapamil, topiramate, nifedipine and naproxen are also used.